Add GFM autocompletion for MergeRequests

Requested
[here](http://feedback.gitlab.com/forums/176466-general/suggestions/5507440-auto-complete-merge-requests-in-gitlab-markdown).

Update gitlab_git to 5.7

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

For those of us running self-signed in gitlab-ci it generates 500s SSL_verify errors if you don't have this.

Use new style shell commands

Out Of Beta

change mysql to postgres in some of the docs and scripts

* update deploy.sh, install gem without mysql, now that we want to use postgres instead
* update update_patch.md to assume postgres before mysql
* update ruby.md, to assume postgres

Add index_merge_request_diffs_on_merge_request_id

Added executable file permission to binstubs

Link to consolidated website with https links. Fixes #6017

Feature: reopen closed merge request

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

Added option to remove issue assignee on project issue page and issue ed...

Convert all help files to markdown files in doc directory

Backup Uploads Symlink

DB Reaping Frequency

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

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

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

Thanks to @jojosch for the initial work on the web-hooks.html.haml file!

Files moved:
* Workflow
* help/ssh
* help/webhooks
* help/system_hooks
* help/public_access
* help/permissions

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

Fix Backup Spec

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

fixed typo at the user management help page