remove unused imports
Merge remote-tracking branch 'origin/refactor-db' into refactor-db

* origin/refactor-db:
  fixed test_handler/test_authentication
  solved bugs after receivers became a Reference
  approached receiver Pickle->ReferenceSet
  broke everything!
  rewriting tests for the notification plugin; cleaning up plugin notification system

Conflicts:
	globaleaks/jobs/notification_sched.py
Merge remote-tracking branch 'origin/refactor-db' into refactor-db

* origin/refactor-db:
  fixed some bugs - ReceiverTip and ReceiverFile
Implement unittest for submission with files

Thanks to testing found 2 bugs.