Desktop/Whiteboards/VolumeControl

Problem
All the techno mumble-jumble (10 different mixers, PCM, IEC958...) that the current audio UI exposes should go away and be replaced by some intuitive concepts, such as one master volume control, and one volume control per stream (or maybe one per category, such as music/phone/events). Audio streams need to have some metadata that lets us identify them in the UI, such as application name and icon. Most of these things are in place now in PulseAudio, and just need to be integrated in a nice UI.