This lets us clean up the mess that was in load_object(), but requires
scope: prototype to be added to the service definitions for all types
or methods!
PHPBB3-11103
Create a very basic user loader class to handle querying/storing
user data in a centralized location.
Use DIC collection service for notification types/methods.
Cleanup unused dependencies.
Fix some other issues.
PHPBB3-11103
Now, if there is no row for the user in the user_notifications table,
the user will receive basic notifications. If the user wishes to not
receive notifications, a row must be added with notify = 0.
For other methods besides the basic (e.g. email, jabber) a row must
still be added with notify = 1 for them to receive notifications
PHPBB3-11103
