Added editing, note-off param fixes, scheduler 'fixes'

Editing is not very well tested, but should turn notes off and what not when appropriate.

I had to change the way note-off parameters have their future values scheduled - before, they would immediately start ramping to note-off values, even if the note wasn't actually supposed to go "off" for a little while (the "delay" parameter).

Also, the note scheduler did weird things (like scheduling note offs on every loop pass for every note that ends somewhere after the current position), so I fixed it up a little.
Unfortunately, it's kind of only a fluke that the first note was playing when we reset the loop. So, I moved the loop start and end points 20 ticks forward, which is very hacky but still makes the note play for now. I think one of us should probably fix the loop scheduling stuff tomorrow.