Change url /admin to /djangoadmin to deploy with GCWeb
WIP: Add PhpbbAuthenticationMiddleware for phpbb session cookies

WIP: We do not check if the session is (still) valid (auto login,
timeout, HTTP Agent).

* Check if there is a phpBB session cookie
* Read the session id and get the corresponding phpBB user
* Add an OneToOneField 'django_user' to abcapp.models.Player and
  recreate the migrations (cause we cannot give a default value).
* Make sure we have the associated django User and
  abcapp.models.Player Object.
* Sync the username and the email address to the django
  user.
* Set the django user as the user