Stereo sound output

[JD557]

Right now, it's only possible to play and manipulate Mono sound.

It should be possible to at least use stereo clips.

Maybe more channels would be ideal, although I don't think it's worth going over 6 channels (surround 5.1). Still, if this for some reason is cumbersome , let's go first with just 2 or 3 channels and call it a day.