When retrieving the Notification ACLs, all specifying which ACLs to filter on
Expose in the internal API the ACLs filter for the notify function
Expose the acls option from the notify method in _bz_notify_cache
Add a api_notify_all endpoints

This endpoints lists for each package every users having at least 1 ACL
Adjust the documentation of the api_notify endpoint to reflect what it is
Add unit-tests for the api_notify_all endpoint
Actually do forward the acls arg to the backend