diff layer/TimeInstantLayer.h @ 21:3a506d25d95a

* Add command history class, and basic undo/redo menus.  No actual commands
  to undo/redo yet.  Selecting the placeholders sometimes seems to cause
  a crash, so this looks a little uncertain so far.

* Add Rename Layer

* Remove models from playback when their layers are removed (and ref counts
  hit zero)

* Don't hang around waiting so much when there's work to be done in the audio
  buffer fill thread

* Put more sensible names on layers generated from transforms

* Add basic editing to time-value layer like existing editing in time-instants
  layer, and make both of them snap to the appropriate resolution during drag