Get rid of Gitlab::ShellEnv

Remove obsolete code we once needed for Grack and satellites.

See merge request !4673

Resolve "Change admin navigation to match new UI"

## What does this MR do?
Moves admin navigation to layout nav to match Project, Groups, and Profile navigation

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

## What are the relevant issue numbers?
Closes #18338

## Screenshots (if relevant)
![Screen_Shot_2016-06-14_at_10.26.40_AM](/uploads/f0b8c8b259da16d929be2b36e8eeafb8/Screen_Shot_2016-06-14_at_10.26.40_AM.png)
![Screen_Shot_2016-06-14_at_10.26.44_AM](/uploads/07d9ece2063dfcfec1f0f2647d8ee782/Screen_Shot_2016-06-14_at_10.26.44_AM.png)
## Does this MR meet the acceptance criteria?

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

See merge request !4650

Prevent default disabled buttons and links.

## What does this MR do?
Prevents default action for disabled buttons and links. If the element has `.btn` and `.disabled` at the same time, its default action will be prevented.

## Are there points in the code the reviewer needs to double check?
Yes. Is there a better way to do that?

## Why was this MR needed?
Right now we can click disabled links and it cause some troubles like in #18079.

## What are the relevant issue numbers?
Fixes #18079

## Screenshots (if relevant)
![disabled-click](/uploads/48b58ce130f843e530e62632bcc27436/disabled-click.gif)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- [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 !4658

Show number of processed MRs in milestone page

closes #14025 

![Screen_Shot_2016-05-02_at_6.20.34_PM](/uploads/9208e58c0e0c77133bd73332ee3b3342/Screen_Shot_2016-05-02_at_6.20.34_PM.png)

See merge request !4006

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Add index on `requested_at` to the `members` table

See merge request !4679

Fixed issue with MR buttons being in a group

## What does this MR do?

Fixes design issue with the buttons in the merge request widget

## Screenshots (if relevant)

![Screen_Shot_2016-06-09_at_14.13.32](/uploads/44ac4175f5a97a8d7baf97be6eebc684/Screen_Shot_2016-06-09_at_14.13.32.png)


See merge request !4562

Check if the Users table has exactly one user limiting the whole set

## What does this MR do?

Limit the query set so about a full scan for all the rows on the users table (only scan to records)

#18225 

See merge request !4492