Sets up paper_trail tracking in important models
and add conference_id to versions for storing conference_id
of conference related objects as metadata.This will help in querying
for versions related to conferences.
Fix issues with factories & event types initialization.Import paper_trail testing helpers
Fix bug: Creating an event creates a useless version with event update
Add revert and view changes features to revision history
For the schedule versioning in the admin interface (having multiple possible shcedules) we need to change some models and associations. It has also been create a rake:move_events_attributes task to migrate the data.
User Interface addapted to make use of the introduced associations and models
* Consistent route/model/controller/view layout
* Get rid of unused photos, speakers, dietchoices, social_events controllers
* Drop unused :public from Rooms and :description from CallForPapers
