HQLPARSER-4

The change comprises:

* New artifact _hibernate-jpql-testing_ which provides a JUnit runner for grammar tests
* Using this new runner instead of GUnit for the existing tests
* Enhancement of the test grammar to allow for organizing tests into groups, using that to organize the existing tests

I didn't notice any problems with the new runner in Eclipse nor Gradle. Note that the test grammar doesn't support all GUnit features, only those which are actually used by the existing tests.