Display totalDue for each registration
Pass into AdminDataCtrl & AdminDetailsCtrl the current permission for the logged in user on this conference.
Display and conditionally allow for update to total due on admin screen
 - Add a directive <total-due>
 - In RegistrationCache add a method to update a Registration and make sure to copy objects when putting them into the cache
 - Add a modal window view and controller for actually updating the total due