fix massedit bug

in case where the first arg in a MassEditU is not actually an UMap, it
should search for the first one that is.
correction in dust UMap
improve UMarker pause function
allow multiple score files to be opened at once
make special method for score space bar function
better zooming for large scores
update comments on various xSoundFile Udefs
add trigSoundFile Udef

plays a soundfile on a trigger