(Bug 44544) Statements are no longer an experimental feature

- patch set 2: use correct bug number
- patch set 3: enable required/related API modules and special pages as well
- patch set 6: 'Special:EntityData' is experimental as well as 'language terms' feature

Change-Id: I257eb917973d9dc29bec7ff9c5c262429f8ef474
Merge "(Bug 44544) Statements are no longer an experimental feature"