Improve MoveGeneratorTest

Hey Bill!

I tried to figure out how to improve your move generator test by using the new move generator tool from JCPI. This pull request adds a new toGenericBoard() method to the Board class which will be used by the move generator test. I've added a new findMissingMoves() method to the test which will print out all missing and illegal moves for a specific board. You can test it yourself by e.g. not generating all promotion moves. Seems like your move generator is pretty solid already... Oh well!

Cheers,
Poky