This commit introduces Releases API under /api/v4/projects/:id/releases
* We are introducing release policies at project level.
* We are deprecating releases changes from tags, both api and web
interface.
* Tags::CreateService no longer create a release
This feature is controlled by :releases_page feature flag
This commit adds a name to each release, defaulting it to tag name,
keeps track of the SHA when a new release is created and tracks the
current user as release author.
CreateTagService and DeleteTagService where in root namespace, by
following service code organization I moved them in Tags::CreateService
and Tags::DestroyService