Implement per channel volume on channelmix. Extend control on stream to
take an array of values when possible.
Remove name argument from pw_node_new and pw_device_new. We can pass
this as a property instead.
Improve properties on nodes to more closely match what pulseaudio does.
Don't let the monitor do too much with the udev properties but let the
session manager set the description and icon-names.
Remove some change_mask flags for things that don't change in
introspect. Use the flags to mark changes in -cli and -monitor.
Pass some state to convert and channelmix functions. This makes it
possible to select per channel optimized convert functions but
also makes it possible to implement noise shaping later.
Pass the channelmix matrix and volume in the state.
Handle specialized 2 channel s16 -> f32 conversion
