Fix MySQL compatibility in zero downtime migration helpers

## What does this MR do?

This MR fixes MySQL for zero downtime migration helpers introduced in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3860

Closes #17711

See merge request !4239

fix group members api doc: remove emial

"Email" is removed in ae564c97

See merge request !4232

Add health check feature documentation

for https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3888

@virtuacreative @axil 

See merge request !4199

Fix docker registry integration

See merge request !4229

Add README for updating .gitignore templates

Add notes to make it clear that users should not file a MR against a specific file here.

See merge request !4227

fix user.name length in milestones participants tab

Spelling mistake of "length"

See merge request !4206

Fix fork counter ui bug for safari

## What does this MR do?

Fixes UI bug on safari when fork button has blue arrow

## Screenshots 

![Screenshot_2016-05-19_22.10.21](/uploads/d923d8fc6bc12ee8f7052390bd5d7c51/Screenshot_2016-05-19_22.10.21.png)![Screenshot_2016-05-19_22.09.38](/uploads/130eb8b4a09b2ba5b7c5a83fed543dbf/Screenshot_2016-05-19_22.09.38.png)

See merge request !4221

Issuable form due date

For some reason, this was never in the original merge request for due date?

![Screen_Shot_2016-04-22_at_21.49.44](/uploads/7d4e2b07f75a33009e3170fdb076a4bd/Screen_Shot_2016-04-22_at_21.49.44.png)

Closes #15516

See merge request !3895

Fixed issue with enter key selecting wrong option in dropdown

If you search for a label and press enter the dropdown will select the last element rather than the first. This is because the currentIndex is -1 rather than 0

![labels](/uploads/eb29924109947fd63fea32e21471f05a/labels.gif)

Closes #17630

See merge request !4210

Fixed issue with merge button color

![Screen_Shot_2016-05-19_at_12.51.35](/uploads/a2768908553961e88c5a8f0e1f343078/Screen_Shot_2016-05-19_at_12.51.35.png)

Closes #17644

See merge request !4211

Wrap "No groups found" message with a .nothing-here-block

The "No groups found" message's style is inconsistent with the other empty messages.

## Screenshots

### Empty groups
![Screen_Shot_2016-05-13_at_13.40.34](/uploads/1447c5f60cde7d50d6f8f07c41704e5c/Screen_Shot_2016-05-13_at_13.40.34.png)

### Empty projects
![Screen_Shot_2016-05-13_at_13.40.30](/uploads/c21ff093f3d6bdbafecf7b075fa33d3c/Screen_Shot_2016-05-13_at_13.40.30.png)

See merge request !4137

Allows MR authors to have the source branch removed when merging the MR


closes #13191 

The location of the checkbox might not be optimal so any feedback is welcome. Any other feedback too obviously.

Screenshot:
![Screenshot_2016-02-17_21.25.24](/uploads/a9c3eaafb39c6f5b4f0949a2278af6da/Screenshot_2016-02-17_21.25.24.png)

See merge request !2801

# Conflicts:
#	app/services/system_note_service.rb

current_user.confirmed_at.present? => current_user.confirmed?

fixes: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3862/diffs#4f7b76b1197d6fb073f77957b3b7b70d921ed7e7_42_41

See merge request !4225

Implement special GitLab markdown reference for milestones

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3453 by @eReGeBe, with two additions:

- Move changelog item to 8.8
- Fix cross-project milestone ref with invalid project, like https://gitlab.com/gitlab-org/gitlab-ce/commit/f7348cd348ad8f4a18d74dd668283a4e236f5790 did for labels

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/13829

See merge request !3897

Fix group visibility level migration in case all visibility levels are restricted

fixes #14632 

See merge request !4107

Let users set notification levels in projects which they are not members

Fixes #9013 

See merge request !3986

Add .gitignore dropdown when creating a new .gitignore file
Signed-off-by: Alfredo Sumaran <alfredo@gitlab.com>

Fix Error 500 when attempting to retrieve project license when HEAD points to non-existent ref

Closes #17537

See merge request !4151

Use extended regexp flag for `git grep`-ing files

Closes #3055

See merge request !4203

A access token -> An access token