the UPnP device goes away - same as for HTTP POST
- Stuff the port mapping requester into a thread so it doesn't
delay everything for several seconds
- Handle UPnP devices that return IP = 0.0.0.0
- Better HTML output when no IP found
- Tweak logging
- Set Disposer thread name
- Keep the control point running after we find an IGD,
so that we get notifications of it leaving or
coming back or replaced.