wordsearch changes and tests

This started out as me just adding more unit tests.  I then realized that I was doing the wrong thing in the case where you spell the right word but keep going.  I refactored wordsearch so that instead of having a finish, we just run through all the steps, and then see if we match the search word.

It also turned out the drawMapTiles test wasn't really running properly, which led to a little more refactoring there.
It might cause Beatles-style subliminal messaging hysteria. Safest to keep letters pseudo-random.