Fix typo in gitlab-workhorse header

See merge request !5891

Disable “issue by email” feature until it uses a different token

Separate token being worked on in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5914, but too late for 8.11.

See merge request !5915

Koding Integration

## What does this MR do?

Will provide Koding integration with GitLab services. Forked from !4914.

## Are there points in the code the reviewer needs to double check?
I've introduced new layouts which might not be necessary, first time contributor. 

## Why was this MR needed?
We're planning to ship Koding with GitLab.

## What are the relevant issue numbers?
#12759 #14698 

## Screenshots (if relevant)

### Screencasts

http://recordit.co/BDMbhwgxPD
http://recordit.co/By0qiz1ClC

### Enable Koding in Application Settings

![image](/uploads/73a69421105c03aa2b0b47e2617d3fbc/image.png)

### Koding Dashboard
![image](/uploads/6c7dda34792280c0e4791e36af4eba11/image.png)

### Set up Koding Stack
1 - ![image](/uploads/d5c2b93f8e61b5cbffdb06f0267d485f/image.png)
2 - ![image](/uploads/44d9a9b574b8ac0c5eb553fb9653d5da/image.png)

### Run on Koding on Project Page

![image](/uploads/7d2b46221009074ffff75d66d5a1a555/image.png)

### Run in IDE on Merge Requests
![image](/uploads/65eed90c34c34b5fe7ad29ef9c717640/image.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5909

Koding: #index: landing page for Koding integration

If enabled it will provide a link to open remote Koding instance url
for now we are also providing the sneak preview video for how
integration works in detail.

Repository: check whether .koding.yml file exists on repository

Projects: landing page: show Run in IDE (Koding) button if repo has stack file

Projects: MR: show Run in IDE Koding button if repo has stack file on active branch

ProjectHelpers: add_koding_stack: stack generator for provided project

With this helper we will auto-generate the required stack template
for a given project. For the feature we can request this base template
from the running Koding instance on integration.

Currently this will provide users to create a t2.nano instance on aws
and it'll automatically configures the instance for basic requirements.

Projects: empty state and landing page provide shortcuts to create stack

projects_helper: use branch on checkout and provide an entry point

This ${var.koding_queryString_branch} will be replaced with the branch
provided in query string which will allow us to use same stack template
for different branches of the same repository.

ref: https://github.com/koding/koding/pull/8597/commits/b8c0e43c4c24bf132670aa8a3cfb0d634acfd09b

projects_helper: provide sha info in query string to use existing vms

With this change we'll be able to query existing vms on Koding side
based on the commit id that they've created.

ref: https://github.com/koding/koding/pull/8597/commits/1d630fadf31963fa6ccd3bed92e526761a30a343

Integration: Docs: Koding documentation added

Disable /koding route if integration is disabled

Use application settings to enable Koding

Projects_helper: better indentation with strip_heredoc usage

Projects_helper: return koding_url as is if there is no project provided

current_settings: set koding_enabled: false by default

Koding_Controller: to render not_found once integration is disabled

Dashboard_specs: update spec for Koding enabled case

Projects_Helper: make repo dynamic

ref: https://github.com/koding/koding/pull/8597/commits/4d615242f45aaea4c4986be84ecc612b0bb1514c

Updated documentation to have right format

Do not escape URI when extracting path

## What does this MR do?

- remove escaping of URI parameters after they have already been unescaped in `ExtractsPath`
- remove spec that is relying on that behavior

## Why was this MR needed?

- spaces in directory names were escaped leading to 404 errors on repository files page

## What are the relevant issue numbers?

fixes gitlab-com/support-forum#952, #21106

See merge request !5878

Show wall-clock time when showing pipeline

## What does this MR do?

Show wall-clock time when showing pipeline instead of cumulative builds time.

Closes #17007

See merge request !5734