Add approval required todos

Ports the 'approval required' todo type from EE - https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/547

See merge request !5217

Resolve "Possible sidebar improvements based"

## What does this MR do?
Cleans up the sidebar

## Are there points in the code the reviewer needs to double check?
@dzaporozhets it looks like your screenshot has more padding on the left and right of the sidebar, but if you do that then the hamburger icon doesn't match the placement on the top nav, and it makes it look like icon is shifting back and forth. 

## What are the relevant issue numbers?
Part of #19659 

## Screenshots (if relevant)
![nav](/uploads/693d8a21bac464fc7dd40a51cb7dccda/nav.gif)

See merge request !5211

Remove Hound CI and Teatro config

## What does this MR do?

Since we moved to gitlab.com we don't use Hound CI and Teatro anymore. Instead we have rubocop.



See merge request !5089

Optimistic locking for Issue and Merge Requests

## What does this MR do?

It implements Optimistic Locking http://api.rubyonrails.org/classes/ActiveRecord/Locking/Optimistic.html for Issues and MRs but in a bit custom way. We use it for cases when either title or description field is involved in the change.

## Why was this MR needed?

We have to prevent data losing.

## What are the relevant issue numbers?
https://gitlab.com/gitlab-org/gitlab-ce/issues/12940

## Screenshots (if relevant)

![Screen_Shot_2016-07-09_at_15.33.02](/uploads/2efbe547a12fda93bce347fa711438d7/Screen_Shot_2016-07-09_at_15.33.02.png)


See merge request !5146

Cache todos pending/done dashboard query counts

See #19273

See merge request !5175

Remove unused RelativeUrl spec support file

See merge request !5207

Bump gitlab-workhorse version for !5094

I think I've created this merge request shortly after I committed this, but it's missing now??

See merge request !5214

Fix GitHub client requests when rate limit is disabled

## What does this MR do?

GitHub Rate Limit API returns 404 when the rate limit is disabled. In this case we just want to return gracefully instead of spitting out an error.

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

No.

## Why was this MR needed?

GitHub importer fails when rate limit is disabled in GitHub Enterprise.

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ee/issues/697

## Does this MR meet the acceptance criteria?

- [X] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- 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)
- [ ] 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 !5191

ObjectRenderer uses read_multi to read cache

## What does this MR do?

Get cache rendered content in bulk

## What are the relevant issue numbers?

#19273

## 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~~
- 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 !5096

Remove the group avatar link.

## What does this MR do?
For group pages, e.g. https://gitlab.com/groups/gitlab-org, I see no reason to link to the avatar image itself when clicking on the avatar.

If the user really wants to open the image, they can do so by right clicking and opening the image in a new tab.

As mentioned in https://gitlab.com/gitlab-org/gitlab-ce/issues/12806#note_12976019.

cc: @fatihacet @alfredo1 

See merge request !5196

Prefer string for describe as of:

https://gitlab.com/gitlab-org/gitlab-ce/blob/b7ba5fa06bfb434c9227a2175f936fc31fd3444f/doc/development/gotchas.md#dont-describe-symbols

See merge request !5202

Refactor permissions.md

- Move `permissions/permissions.md` to `user/permissions.md`
- Remove wrong assumptions about group visibility
- Merge CI `ci/permissions/README.md` to `user/permissions.md`

## What are the relevant issue numbers?

Resolves https://gitlab.com/gitlab-org/gitlab-ce/issues/19414

See merge request !5210

For group pages, e.g. https://gitlab.com/groups/gitlab-org, I see no reason to link to the avatar image itself when clicking on the avatar.

If the user really wants to open the image, they can do so by right clicking and opening the image in a new tab.

Reset project pushes_since_gc when we enqueue the git gc call

## What does this MR do?

Reset counters just when we really enqueue the `git gc` command. So as this is part of the `#execute`method we throttle the enqueue and the reset (database statement) as we throttle the `#increment!` call. And we only call `#execute` if it's needed.

## What are the relevant issue numbers?

Closes #19711 

## 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~~
- 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 !5201

Rename profile navigation tab 'Personal Access Tokes' to 'Access Tokens'

For https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3749#note_12994215. We should not use more than 2 words for tab name 

See merge request !5187