model/auth: Added has_permission() method
model/auth: Added is_manager() method
flask: Removed groups and permissions from request.identity
views/notifications: Add notification count to g object
flask: Reduced request.identity to None or User instance
views/login: Inject current_user into g object

We don't use an anonymous user here though. The variable will be set to
None if no user is logged in.
Merge pull request #78 from Turbo87/request-cleanup

Cleanup of the request.identity dict