Add container registry support
Tasks:
- [x] Merge docker/distribution authentication service: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3787
- [x] Implement Docker Registry API
- [x] Show a list of docker images in GitLab
- [x] Remove registry repository on project deletion
- [x] Support project rename, move and namespace rename
- [x] Use token when connecting the registry
- [x] Allow to delete images from GitLab
- [x] Support pushing from GitLab CI (gitlab-ci-token / $CI_BUILD_TOKEN)
- [x] Support GitLab Runner pulling for public repositories
- [ ] Support GitLab Runner pulling for private repositories
- [x] Add tests for Docker Registry API
- [x] Add tests for a views
- [x] Make texts nicer
- [x] Implement a backup support
- [ ] Create administration documentation https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4141
- [ ] Create user documentation
See merge request !4040
Auto-set title for branches created from issues
This sets the title for a new MR to 'Resolves "$issue-title"' when:
- The source branch for the MR begins with a value iid.
- The MR has more than one commit in its diff (if there's one commit, keep using the commit's first line).
- The iid does not point to a confidential issue.
Single commit:

Multiple commits:

Confidential issue:

cc @DouweM @zj
Closes#14564
See merge request !3966
If a branch starts with an issue's IID, followed by a hyphen, the
description will be updated to say that is closes the issue. This also
updates the title of the merge request to 'Resolves "$issue-title"', as
long as:
- There is more than one commit in the merge request (if there is only
one commit, the commit's title will be used as before)
- The issue's IID is valid for the project