do not remove merge requests when fork project destroyed

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Render valid message when MR source or target branch was removed

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Add new methods to MR to check if source or target branch exists

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Proper erro message for MR when fork removed

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Use MR#source_project_path method instead of merge_request.source_project.path_with_namespace

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Allow close of broken MR

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

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'bug/mr_duplicate_iids' of /home/git/repositories/gitlab/gitlabhq
Merge branch 'master' of github.com:gitlabhq/gitlabhq