Adding an action (can be invoked from the admin change list page) to create or update filersets
The logic to create/update filersets is now place in a custom model manager for the Set model. The manage.py command was rewritten to invoke the logic in the new manager. The set model was extended with a is_processed flag that defaults to False. Only when the processing of new filersets has finished this flag is set to true, so querying the set model with a condition is_processed=True ensures that sets are truely available (instead of being created but not processed)