Add unit test to demonstrate a bug in the dynamic query builder, where specifying that the id of some relation is null will always return 0 results.

Updating HSQLDB from 1.8 to 2.3 (otherwise calling save() doesn't work)
Fixing issue - problem was that the dynamic query builder was constructing the wrong kind of join
Merge pull request #1 from petergeneric/master

Fixes bug with dynamic query builder where relation.id=_null would return empty resultset