Changes to user accounts:
Currently in the login framework, the user is identified by one
MasterAccount (aka RTFAccount) record and one or more AuthProviderAccount
(aka APAccount) records

The MasterAccount class has been removed.
The AppUser class has been modified to support all operations handled by
the MasterAccount class.
The AppUser class uses Objectify for persistence, however persistence
operations for AuthProviderAccount are still handled without Objectify.

Known issues:
on login success with facebook, email is not being received in json
log.fine does not seem to work on appengine logs