Switching speakers

It would be great if groovebasin allowed to switch speakers. E.g. if I have a 5.1 audio interface, and I put 2 speakers into the livingroom and one into the kitchen. Now I would like to switch between the livingroom setup and the kitchen setup in the groovebasin webinterface/remote app. Another use case might be playing cinema soundtracks in 5.1 and normal hifi audio in 2.0. So this is not only about switching between speaker pairs, but also about switching mono/stereo/surround.

(In terms of audio quality, the livingroom/kitchen setup especially makes sense if you have a good audio interface with balanced audio output in the livingroom, and use that to drive active speakers in the kitchen, instead of putting something like a Raspberry Pi with lower quality audio output there, see https://en.wikipedia.org/wiki/Balanced_audio).

This is related, but not the same as #313 -- that one is about streaming digital data, this here is about switching the analog audio signal to different outputs (through PulseAudio or similar frameworks). Both are solutions for multiroom setups.