Undo redo memento

-Added preliminary undo redo functionality using the memento pattern.
-Most top level files moved into a WackaUML package
-Some adjustments to the deleteSelf and clone functions
-Undo redo is fully functional for adding a new class, moving a class, and renaming a class
-Undo redo is partially functional (very buggy still) for method add, member add, new relationship, and move relationship.