* change controller.Notebooks.load_note_revisions() to select and return User_revision objects
* change controller.Notebooks.save_note() to use User_revision objects for new_revision and previous_revision as well
* update client to deal with new load_note_revisions() return values (make sure all uses of revisions_list are updated)
* update client to deal with new new_revision/previous_revision
* update changes pulldown to show username along with each timestamp
* update model.Invite to load redeemed_username along with redeemed_user_id
* display the redeemed username next to each email address in the "share this notebook" note
* Each model.User now has a current storage bytes and a rate plan.
* model.User.to_dict() updated accordingly.
* Minor Scheduler.add() change to bail of the given thread is None.
* controller.Users.current() returns current user's rate plan details.
* controller.Users.update_storage() now takes an optional callback.
* Various methods in controller.Notebooks responsible for calling controller.Users.update_storage().
* Added rate plan details to config/Common.py.
* Added quota utilization colors to style.css.
* Implemented quota utilization calculation and display in Wiki.js.
Still to-do: Return updated storage bytes where appropriate in controller.Notebook and update the
client accordingly.
* Made sure the trash is not exposed by the read-only notebook view.
* Modified model.User.check_access() to consider read-write access to a
notebook to be sufficient for access to that notebook's trash.
* Modified controller.Users so new users are created with a notebook that
has a trash.
* Changed controller.Notebooks so deleted notes go to the trash (if any).