build 20080616

This problem applies to other type of diagrams as well.
- create a class diagram
- drag a package element to the diagram
- drag a class element to the diagram
- create a nested link or containment between the class and package so that the class is contained in the package
- expand the project tree down to the package to see that the class is under the package
- from the diagram, slightly move the class element to a different location on the diagram
- look at the class in the project tree now. the class is no longer under the package.