Parse the module arguments according to the pulseaudio syntax,
not our own syntax (which requires "" around a , delimter). Fixes
audio.position=FL,FR argument.
See #527
Implement a minimal version of the LOAD_MODULE and UNLOAD_MODULE
stream commands. The only supported module for now is the null
sink.
Modules are stored on a per-client bases, so that when clients
are disconnected, the modules they loaded is removed too.
This is enough to allow GNOME Network Displays to register a sink.