Zerberus Trigger::Release

currently the trigger release does not work in the right way. Because it is started in stopped mode (have a look at Zerberus::Trigger) it's envelope gets set to release and the release amplitude max is 0 because the voice was just started (and being in decay state).

Solution would be to tread envelopes a little different during trigger::release - and calculate the sustain in that way that all envelops together are equal to the sample length (this seems how it is done in sforzando)