Shut down the entire application.

def shutdown(self):
        """
        Shut down the entire application.
        """
        logging.info("Shutting down")
        self.closeAllWindows()
        self.notifier.hide()
        self.service.shutdown()
        self.monitor.stop()
        self.quit()
        os.remove(common.LOCK_FILE)  # TODO: maybe use atexit to remove the lock/pid file?
        logging.debug("All shutdown tasks complete... quitting")