CVS: velocity and related events

[Tim Janik <timj gtk org>]

hi all.

i've added velocity editing to the CVS version.
besides the piano roll editor, there's an event
roll now, which can be used to edit various types
of MIDI events, not just note velocity.

i'd apprechiate if those running the CVS version could
give it a try and report problems/give feedback for it.

---
ciaoTJ