Removing manage.py's usage of "dev.settings"

Fixes issues seen with celeryd/celerybeat/and unittest confusion.
splice-server isn't operated in 'dev' mode since it requires apache/mod_wsgi
setting of SSL headers to function which is not faked out with django's runserver
Add mongo port to config file
Added @single_instance_task decorator to restrict celery tasks spawned by different processes to a global single task running at a time