First crack at undo management.
Manual annotation addition can now be undone/redone.
Now restoring the displayed time range and selection when undoing/redoing.
Detecting features is now undoable.
Fixed issues undoing/redoing feature detection.
Manual annotations can be added again.
Merge branch 'master' into undo

Conflicts:
	FeatureReporter.m
	Panels/FeaturesPanel.m
	TempoController.m
Edit menu items are now consistently enabling/disabling.
All feature panel actions are now undoable.
Undo now works better after a feature panel closes.
Fixed problem undoing past feature detection.
Restored missing items to FeaturesPanel action menu.
Moved undo code to the new UndoManager utility class.
Merge branch 'undo'