[WIP] Removing moderated edits

As per #1414 this WP will:

* Ignore the current column on the revisions table
* Replace all the queries that are specifically looking at revisions (like package_list) and have them just query the package model instead (it'll be the same as the current=True revision).
* Remove the ability to view packages and other objects at specific revisions.

Once complete this PR will mean that revisions are not queries during the normal running of the system, although they will still exist and still be recorded (just in case someone wants to migrate them). When created the current = True flag will NOT be set on any of the revision models, instead it is expected whoever does a migration will do so with timestamps.