Use Callback System for sounddevice usage

[steveway]

It might make sense to use SoundPlayer.py on all systems since this does not depend on QT for playback. The only real problem seems to be the volume, while it is playing it can't be changed. But using the Callbacks it is apparently possible to change the volume during playback. https://github.com/spatialaudio/python-sounddevice/issues/159 If we get this to work nicely with all platforms we can just use this for everything.