Implement nvda_not_connected

[tech10]

Hello,
The NVDARemote json protocol has a type, nvda_not_connected which can allow the controlling NVDARemote addon to tell you when a client to be controlled, is connected to the server. I don't think most servers se this in their protocol, but the one I wrote does, and it works very well with the addon. Would you consider implementing this type in the application, so if attempting to use the application with a channel where no clients to be controlled are connected, you can be alerted? I have tested this already in the latest beta, and it doesn't seem to be implemented yet.