Allow manual specification of release date for Releases
Problem to Solve
From @patrikhuber in https://gitlab.com/gitlab-org/gitlab-ce/issues/56969:
The ordering in the Releases page went completely bogus for my project. A minor version released later than a patch version is at the bottom of the page. All the releases show "released 3 month ago". Not true. The date + time that is displayed there is neither the time of the commit nor the tag or anything else from git. Maybe this is the time when I added the "Release notes" on the Tags page...? But certainly I don't want to have the Releases ordered by what time I added the release notes on the Tags page!
Proposal
This issue comes from the fact that we assume the date a release was created is the release date of that release. Instead, we should add an editable release date value for a release and sort by that.