Multi-channel volume and pan control

[Christoph Hart]

You were right. Although the problem was a more generic one: If you activate the KillNote retrigger behavior, it kills also samples that are just started and leaves only the last sample in the crossfade list alive. My example (and every time I used this feature) magically had the KillNote property disabled so I didn't notice it.

This is of course highly counterintuitive so I added a check that doesn't fire the retrigger behaviour if the voice was started with the same event. It's on GitHub now.

This also fixes the velocity X-Fade behavior and actually all cases where one event starts multiple samples (excluding multimic samples) so nice catch!

But it has nothing to do with another sampler and it would highly violate our precious encapsulation principle, so please make sure this problem does not persist.

[d.healey]

Excellent, glad it wasn't just me being mad