Created $wgMWOAuthGrantPermissions and related functions

* Also added a Special:MWOAuthConsumerRegistration/list subpage
  and redid how the /update subpage works to prefill fields.
* Improved field validation for several attributes.
* Various other minor cleanups.

Change-Id: I8e3925b9f0f6eb34a66dde043547ee76858139ab
Merge "Created $wgMWOAuthGrantPermissions and related functions"