Implement remote playback clients

[pdrd]

Enable the playback through a network stream, so that clients can connect with their own playback clients remotely.

This also makes it possible to playback in several rooms with one pynitus server.

[strangedev]

+1

Strictly speaking, this is a feature in https://github.com/strangedev/tinnitus, I will create an issue there.
Once tinnitus supports multiple backends at once, we can start integrating it into Pynitus.