Add GFM autocomplete for labels

Closes #14637 

See merge request !4013

Improve pipeline status in case that pipeline has no jobs

## What does this MR do?

This MR resolves problem with pipeline status when there are no build in pipeline.

This can happen when builds were skipped - for example - by using `only`/`except` keyword in `.gitlab-ci.yml`.

## What are the relevant issue numbers?

Closes #17977

See merge request !4403

Fair usage of Shared Runners

## What does this MR do?

Introduces a fair usage scheduler for shared runners.

It tries to assign builds to shared runner from projects that have the lowest number of builds currently running on shared runners.

**Example 1**:
```
We have following builds in queue:
build 1 for project 1
build 2 for project 1
build 3 for project 1
build 4 for project 2
build 5 for project 2
build 6 for project 3

With the new algorithm we will assign builds in following order:
- We choose build 1, because project 1 doesn't run currently any builds and has the lowest build number from projects that doesn't run builds,
- We choose build 4, because project 2 doesn't run currently any builds and has the lowest build number from projects that doesn't run builds,
- We choose build 6, because project 3 doesn't run currently any builds and has the lowest build number from projects that doesn't run builds,
- We choose build 2, because project 1 as other it runs 1 build,
- We choose build 5, because project 2 runs 1 build, where project 1 runs 2 builds now,
- We choose build 3, because project 1 and runs 2 builds.
```

 
**Example 2**:
```
We have following builds in queue:
build 1 for project 1
build 2 for project 1
build 3 for project 1
build 4 for project 2
build 5 for project 2
build 6 for project 3

With the new algorithm we will assign builds in following order:
- We choose build 1, because project 1 doesn't run currently any builds and has the lowest build number from projects that doesn't run builds,
- We finish build 1,
- We choose build 2, because project 1 doesn't run currently any builds and has the lowest build number from projects that doesn't run builds,
- We choose build 4, because project 2 doesn't run currently any builds and has the lowest build number from projects that doesn't run builds,
- We finish build 4,
- We choose build 5, because project 2 doesn't run currently any builds and has the lowest build number from projects that doesn't run builds,
- We choose build 6, because project 3 doesn't run currently any builds,
- We choose build 3, because project 1, 2 and 3 runs exactly one build now,
```

## Why was this MR needed?

Currently, we are scheduling builds using FIFO. This is catastrophic if there are projects that create a 100-300 jobs, this basically eats most of available shared runners.

## Performance

All this logic is implemented with the help of SQL queries, because this is the fastest way to process 1k-2k pending builds in queue.
It's not the fastest SQL query, because it sorts based on number of running_builds, and this forces to calculate a number of running builds for all dependent projects. However, since we have one/two shared runners that asks every few seconds for builds this should have minimal impact on DB performance.

```
 explain analyze SELECT "ci_builds".* FROM "ci_builds" JOIN (SELECT "ci_builds"."gl_project_id", count(case when status = 'running' AND runner_id = (SELECT "ci_runners"."id" FROM "ci_runners" WHERE "ci_runners"."is_shared" = 't') then 1 end) as running_builds FROM "ci_builds" INNER JOIN "projects" ON "projects"."id" = "ci_builds"."gl_project_id" AND "projects"."pending_delete" = 'f' WHERE "ci_builds"."type" IN ('Ci::Build') AND "ci_builds"."status" IN ('running', 'pending') AND "projects"."builds_enabled" = 't' AND "projects"."shared_runners_enabled" = 't' GROUP BY "ci_builds"."gl_project_id") AS projects ON ci_builds.gl_project_id=projects.gl_project_id WHERE "ci_builds"."type" IN ('Ci::Build') AND "ci_builds"."status" = 'pending' AND "ci_builds"."runner_id" IS NULL  ORDER BY projects.running_builds ASC, ci_builds.id ASC;
                                                                                  QUERY PLAN                                                                        
           
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
-----------
 Sort  (cost=64777.28..64777.29 rows=1 width=1010) (actual time=301.794..302.535 rows=1537 loops=1)
   Sort Key: (count(CASE WHEN (((public.ci_builds.status)::text = 'running'::text) AND (public.ci_builds.runner_id = $0)) THEN 1 ELSE NULL::integer END)), public.ci
_builds.id
   Sort Method: quicksort  Memory: 1423kB
   ->  Nested Loop  (cost=63279.78..64777.27 rows=1 width=1010) (actual time=66.384..298.724 rows=1537 loops=1)
         ->  HashAggregate  (cost=63177.15..63177.30 rows=15 width=15) (actual time=65.641..65.851 rows=187 loops=1)
               InitPlan 1 (returns $0)
                 ->  Seq Scan on ci_runners  (cost=0.00..26963.66 rows=1 width=4) (actual time=1.145..34.381 rows=1 loops=1)
                       Filter: is_shared
                       Rows Removed by Filter: 6965
               ->  Nested Loop  (cost=0.00..36186.34 rows=2715 width=15) (actual time=0.065..29.717 rows=1710 loops=1)
                     ->  Index Scan using index_ci_builds_on_status on ci_builds  (cost=0.00..8913.95 rows=3577 width=15) (actual time=0.051..12.012 rows=2583 loops
=1)
                           Index Cond: ((status)::text = ANY ('{running,pending}'::text[]))
                           Filter: ((type)::text = 'Ci::Build'::text)
                           Rows Removed by Filter: 1219
                     ->  Index Scan using projects_pkey on projects  (cost=0.00..7.61 rows=1 width=4) (actual time=0.003..0.004 rows=1 loops=2583)
                           Index Cond: (id = public.ci_builds.gl_project_id)
                           Filter: ((NOT pending_delete) AND builds_enabled AND shared_runners_enabled)
                           Rows Removed by Filter: 0
         ->  Bitmap Heap Scan on ci_builds  (cost=102.63..106.64 rows=1 width=1002) (actual time=1.216..1.231 rows=8 loops=187)
               Recheck Cond: ((gl_project_id = public.ci_builds.gl_project_id) AND ((status)::text = 'pending'::text))
               Filter: ((runner_id IS NULL) AND ((type)::text = 'Ci::Build'::text))
               ->  BitmapAnd  (cost=102.63..102.63 rows=1 width=0) (actual time=1.201..1.201 rows=0 loops=187)
                     ->  Bitmap Index Scan on index_ci_builds_on_gl_project_id  (cost=0.00..10.52 rows=241 width=0) (actual time=0.406..0.406 rows=1944 loops=187)
                           Index Cond: (gl_project_id = public.ci_builds.gl_project_id)
                     ->  Bitmap Index Scan on index_ci_builds_on_status  (cost=0.00..91.78 rows=3089 width=0) (actual time=0.652..0.652 rows=3362 loops=187)
                           Index Cond: ((status)::text = 'pending'::text)
 Total runtime: 303.832 ms
```

## Specific runners

It doesn't affect the specific runners which still serve builds FIFO.

@stanhu @markpundsack @yorickpeterse What do you think?


See merge request !4634

* master: (198 commits)
  Set inverse_of for Project/Services relation
  Fix admin hooks spec
  Prevent default disabled buttons and links.
  Add index on `requested_at` to the `members` table
  Rearrange order of tabs
  Fix admin active tab tests
  Show created_at in table column
  Nest li elements directly under ul
  Move builds tab to admin overview
  Add monitoring link with subtabs
  Add sub links to overview
  Add counter for abuse reports
  Remove admin layout-nav counters
  Move admin nav to horizontal layout nav
  Eager load project relations in IssueParser
  Use validate and required for environment and project
  Award Emoji can't be awarded on system notes backend
  Get rid of Gitlab::ShellEnv
  Update CHANGELOG.
  Fix project star tooltip on the fly.
  ...

Conflicts:
	app/services/ci/create_builds_service.rb

Get rid of Gitlab::ShellEnv

Remove obsolete code we once needed for Grack and satellites.

See merge request !4673

Add environments and deployments

This MR is a continuation of https://gitlab.com/gitlab-org/gitlab-ce/issues/17009.

The current implementation is as follow:
1. We have two new tables: `environments` and `deployments`.
2. We have a new tab: `Environments` under `Pipelines` where you can see all you environments and add a new one.
3. We add a new option to `.gitlab-ci.yml` to track where we should create a deployment for environment.
4. If environment in `.gitlab-ci.yml` is specified it will create a deployment. **If environment does not exist it will be created.** (this got changed)
5. The deployment is always successful and shows the time of the action, in that case a build that presumably should do deployment. In the future we could extend deployment with statuses: success, failure. We could extend deployments with information that this is partial or full deployment.
6. User have to create environments that he will track first.
7. User can remove environments.
8. User can retry/rollback past deployment (in that case we retry past build). The new build when succeeds it will create a new deployment.
9. Currently environment have only one parameter: `name`. In the future it should have: `variables`, `credentials` and possibly `runners` and maybe other resources.
10. Currently deployment have this parameters: `sha`, `ref`, `deployable (in this case a build)`, `user (who triggered a deployment)`, `created_at`.

The `.gitlab-ci.yml`:
```
deploy to production:
  stage: deploy
  script: dpl travis...
  environment: production
```

What needs to be done:
- [x] Write initial implementation
- [x] Improve implementation (@ayufan)
- [x] Write tests (@ayufan)
- [x] Improve UX of the forms (cc @markpundsack) - reviewed by @markpundsack
- [x] Improve implementation of the views (cc @jschatz1) - done by @iamphill 
- [x] Write .gitlab-ci.yml documentation for `environments` - done by @ayufan
- [ ] Write user documentation (@ayufan and @markpundsack)

See merge request !4605

Manually create todo for issuable

## What does this MR do?

Adds a button to the sidebar in issues & merge requests to allow users to manually create a todo item themselves.

## What are the relevant issue numbers?

Closes #15045 

## Screenshots (if relevant)

![Screen_Shot_2016-06-07_at_09.52.14](/uploads/00af70244c0589d19f241c3e85f3d63d/Screen_Shot_2016-06-07_at_09.52.14.png)

![Screen_Shot_2016-06-07_at_09.52.06](/uploads/e232b02208613a4a50cff4d1e6f119ff/Screen_Shot_2016-06-07_at_09.52.06.png)

![Screen_Shot_2016-06-07_at_09.51.14](/uploads/f1d36435d49ab882538ae2252bec8086/Screen_Shot_2016-06-07_at_09.51.14.png)

See merge request !4502