Convert GFM reference handling to html-pipeline filters

- `Gitlab::Markdown` is now much cleaner
- Better separation of concerns
- Cleaner, less brittle, more maintainable specs for each reference type.
- Label references actually work!

See merge request !1753

add environment variable force to the documentation

7.10 requires gitlab-shell 2.6.2.

Fixes #1467.

See merge request !552

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

Conflicts:
	app/controllers/import/google_code_controller.rb

Fix some issues with Google Code importer

Thanks, @mrtux, for reporting all of these.

See merge request !551

Update gitlab-grack to 2.0.1 to get unicorn to stop creating zombies.

Addresses #1461 and private issue https://dev.gitlab.org/gitlab/gitlabhq/issues/2253.

This regression was introduced between 7.9 and the 7.10 rcs, so no changelog item for 7.10 proper.

cc @JobV @jacobvosmaer

See merge request !546

upgrade hipchat

Fix "Cannot move project" error message from popping up after a successful transfer

The JavaScript click handlers were never being removed, leading to duplicate requests when attempting to transfer a project to another namespace. The first transfer would succeed but the subsequent ones would fail, leading to the error message saying, "Cannot move project".

![image](https://gitlab.com/stanhu/gitlab-ce/uploads/0c9f61294291514e0c2a48c204b6a1aa/image.png)

I attempted to write a unit test for this, but it was taking me too long to get it right.

Closes #1448 and #1128

See merge request !548

Multiple event handlers were firing, causing multiple form submissions.

Closes #1448 and #1128

Also, tables! (╯°□°）╯︵ ┻━┻)

Prior it would return the project from the current context, which wasn't
the intended behavior.

[ci skip]

This will allow for the removal of a lot of duplication from the
reference filters.

For simplicity's sake, since we're testing the actual referencing, we
just force the permission check to always be allowed.