[API] add parent_ids to specific commit informations
Created by: bobot
The current api does not indicate the parents of a commit, which is a very useful information for moving inside the commits history. This merge request add this information to the api for a specific commit in order to not bloat the generic version.
Also add comitted_date
and authored_date
information because created_at
is ambiguous (eg. #4666 (closed))