Two Sequence types

We tried to be smart and have one types of `Sequence` , the Tulip one and the AMY one. It's more confusing than not. I'll make a TulipSequence that's only for general python, but follows the same AMY sequencer clock at the same tempo and PPQ. That can be used for graphical updates and games and etc. Then AMYSequence will be only for AMY events -- synth, MIDI, etc.