If you select several items and delete them, invoking undo does not undo all of
the deletions, only one at a time.  It is very inconvinient to invoke undo for
each item especially since it only took one delete to remove all selected.

To Reproduce:
Using Milestone7b
1. Open OTA_TravelItinerary schema
2. In schema view expand complex types node.
3. Select several complex types and press delete
4. Invoke Undo any way you want
observe that each time only one item is returned.