Use /listDevices and /getZones

[tfeldmann]

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The library should discover the first device via a multicast and then read in the zones and devices from the lists /listDevices and /getZones.

[tilltnet]

I have implemented a music zone management feature in my raumfeld remote rf.wr using python-raumfeld, /getZones /connectRoomToZone and /dropRoom. Making those commands available in the library would be really helpful! I have made a small change to the output behaviour of discover() in order to handle a specific problem. With my patch it is possible to 'rescue' the system if no rooms are created, for example after a fresh reboot without any contact with the official Apps. Please have a look at the patch in my fork and consider including this behaviour in the library.