Initial work towards true multi-item editing as a single logical unit.
Implement multi-item smoothing...
More functionality for working with multi-items
Somewhat working multi-item piano roll editing...

There are probably still lots of bugs in there...
Begin moving certain variables to global scope
More multi-item work
More fixes...
Fixes to multi-item snap settings...
More fixes, and still many more bugs...
Even more fixes...  I think it's getting halfway usable now...
Begin restoring the list editors back to how they were before, I'm
going to leave them functioning exactly as before, rather than trying
to change everything at the same time...
Add some of the original controls back to the list editors only...
Nearly back to working list editors again...
More fixes...
Even more fixes and some rule-changes to prevent user stupidity...
Once I iron out the last few bugs, this is ready to be  merged...
Ensure the arrow cursor is restored on double-click or delete events...
This should fix most of the snap issues...
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