HSQL parser support for LIMIT PARTITION ROWS <N> EXECUTE (DELETE ...)

These changes make it so our HSQL parser extensions will parse a DELETE statement in a LIMIT PARTITION ROWS constraint.  The text of the DELETE statement is then added to a new table attribute in the catalog.

I also added a little more testing, and added the new syntax to the DDL for the SQL features junit test.

There still remains to be done the middle piece that connects the front and back end.  I had thought that the middle piece would be straightforward enough to finish up here, but I was sadly mistaken.
Yes, I think you're right.  I'll fix it.