[#62] Ensure dbus services are present

Created by: elbenfreund

This PR uses Gio.bus_watch_name to make sure appearing/vanishing hamster dbus services are handled accordingly. Right now we only act on vanishing/not running services by triggering disable. Future itteration could consider being a bit more forgiving, but for now this should help to make potential issues attributed to the extension that are really caused by the dbus service more clear.

Closes: #62 (closed)