Modeler sync function adds extraneous ObjRelationships inside the class hierarchy

Per this discussion http://www.mail-archive.com/user@cayenne.apache.org/msg09253.html , when you use Modeler Db->Obj sync functionality within classes with vertical inheritance, the Modeler would add a bunch of extraneous ObjRelationships between base class and subclasses. Sync algorithm should be smarter about inheritance.