More consistent event names
We're storing as services.issues_events and services.merge_requests_events, that is issues and merge_requests are plural. However, the event name is singular like issue and merge_request. On the other hand, all other event names are all singular.
This caused that we need some special rules in a number of places, namely the view form.
!5861 (closed) is an attempt to make this consistent without changing the data. However, it seems it's causing even more special rules. Please see the comment at: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5861#note_14057068
So to solve this once and for all, we should probably rename the columns, namely use services.issue_events and service.merge_request_events then we could remove all the special rules.
This issue is created in request in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5620#note_14081185