Hide mr close button for comment form if merge request was closed or inline comment

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

Conflicts:
	app/views/projects/merge_requests/_show.html.haml
Added option to remove issue assignee on project issue page and issue edit page

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

Conflicts:
	CHANGELOG
Feature: reopen closed merge request

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

Conflicts:
	app/views/projects/merge_requests/_show.html.haml
	app/views/projects/merge_requests/show/_mr_title.html.haml
Add tests to reopen MR

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Hide close mr button

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
 Merge branch '6-6-5-patch' into '6-6-stable'

6.6.5 patch

* adds ability to reopen mr
* adds ability to remove issue assignee
* removes close button from diff comment form
Version 6.6.5

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch '6-6-stable' of github.com:gitlabhq/gitlabhq into 6-6-stable