bugfix: added djangoldp_notification activity types to ActivityQueueWorker logic

Closes djangoldp-notification#36 (closed)

@jbpasquier this MR is ready, could you test to confirm it fixes the linked issue in djangoldp_notification please?

I fixed it by adding the creation and deletion activity types to the existing ActivityQueueWorker logic. I chose this solution because it impacts existing code less than using create and delete types in djangoldp_notification