Add a module that retrieve mute status and volume (left, right, mono)
from pulseaudio. Unfortunately, this module is really, really hacky. It
invokes "pactl" multiple times to get the status and does some ugly
parsing on the output.
Overall, this is pretty brittle and prone to failure, but as I was not
able to find a decent pulseaudio library for Python... Probably, I
haven't searched hard enough, cannot believe such a thing does not
exist.
