FO-07 Basic private messages

Still a lot of work to do on the views
Some bugs with displaying read/unread conversations
FO-07 Correctly show read/unread messages

Redirect to conversations index when trying to show other users conversations
FO-07 Form checking for new private message
Merge branch 'master_update' into FO-07_Private-Messages

Conflicts:
	app/controllers/users_controller.rb
	db/schema.rb
FO-07 Add autocomplete for recipient

Still needs visual improvements
FD-01 Add pagination to debates listing
Merge branch 'master_update' into FO-07_Private-Messages