DS-2248 XMLUI Delete Community doesn't work

Untested.  I will test it, but I make the patch available now for others to try.

This fixes two things:  (1) have DSO subclass constructors ensure that the embedded TableRow has a table name, to prevent NPE later; (2) decache Collection much later in delete() to prevent the object reappearing in the Context cache and causing spurious test failures.  Plus some tidying-up of surrounding code.