improve delay UMapDef

make sure it starts at the initial position of the input, not at 0.
ukrArgSpec add private and mode
lower maxUndoStates

high numbers cause slow response with large scores
allow zero rate in Buf/DiskSoundFilePlayer
correct sample_and_hold UMapDef

now starts at incoming value instead of zero
add 'crackle' Udef
improve BoolSpec:constrain

can now handle array input
add 'range' type to shared_value Udef
add peak and value_to_range UMapDefs
enable MultiUdefs in MassEdit

can only mass-edit if all the same type
slow down UScoreView updating
disable UScoreEditor undo

until we find the solution for memory leak
Udef.find and Udef.open convenience methods
corrections related to undo functionality

- undo states were double stored when using arrow keys
- buttons would not be disabled when undo/redo history was empty
make UMarker forget score if not needed

so that it isn't copied with at .duplicate
revisit undo system
cosmetic changes and add 'enable' button to score editor undo
shallow copy instead of deep copy for Score undo

deepCopy may take much more memory, while the changes that can be made
in the score editor can all be stored via shallow copy.
create shared_io udef category
Update README.markdown