T154 supervisord xmlrpc

The state of currently running supervisor-managed processes can be viewed using ```sudo supervisorctl```, then the ```status``` command.  Make sure to configure SUPERVISOR_UNIX_SOCKET_FILE in local_settings.py.

Not quite ready as I'd like to add handling for the case where remove_process_group attempts to stop a process that is already stopped (this throws an exception, but we would like to handle gracefully and proceed.  Perhaps check first?).