added more improvements to the infinite undo and reworked existing undo actions to conform to the infinite undo model. fixed per-window undo menu updating, finalized undo actions 1,2,3,4,5,9, and 10. Still need 6,7,8 and a new action 11 (namely apply, canvas apply, to front/back, and rename). Also improved paste behavior to make it more user friendly, particularly within the context of infinite undo.