This class wraps a list of multiple undo actions, and tells them to undo all at the same time.

	initialization
	initialize setChangeList:

	undoing
	undoIt

	adding changes	top
	add: Add an undoable to the change list

	initialization	top
	initialize Initialize this method by creating an empty change list.
	setChangeList:

	undoing	top
	undoIt Undo by undoing all the changes in the change list

	instance creation	top
	new Answer a new instance of the receiver (which is a class) with no indexable variables. Fail if the class is indexable.