asynchronous refactoring

- don't execute celery tasks directly
- introduce optional parameters to fileserver tasks to allow chaining
- handle user/group/key create and delete tasks in new osusers.signals
  class
- adapt unit tests
- change TaskResults model to store the task signatures
- generalize the local settings' logging configuration

gnuviechadmin/osusers/apps.py

@@ -4,6 +4,7 @@ This module contains the :py:class:`django.apps.AppConfig` instance for the
 
 """
 from __future__ import unicode_literals
+
 from django.apps import AppConfig
 from django.utils.translation import ugettext_lazy as _
 
@@ -15,3 +16,6 @@ class OsusersAppConfig(AppConfig):
     """
     name = 'osusers'
     verbose_name = _('Operating System Users and Groups')
+
+    def ready(self):
+        import osusers.signals