Tighten notification triggers; use local qrcodes

 - Make the notification menu listen only to "login" and "logout"
   events, rather than any change on the user object. You should get
   updates for notifications every time you navigate to a page that
   fires a persona login or logout event.
 - Switch to local qrcode generation using jquery.qrcode. Simplifies
   acquisition of qrcodes, doesn't rely on 3rd party, more safe secure
   etc, but an additional 4kb script burden.