Made the sound manager mute controls readable, and got rid of system
enable since it just controls system mute anyway. This was causing
confusion: phantom2 was trying to use both independentlyt casuing the
mute bit to be ignored.
THe Lua interface changes are mostly changing methods to properties,
some renames to make things clearer, and some additional properties for
better control over snapshots.
9e36b6a6d9