Mysql fix and test

Some folks using MySQL ran into a problem where a TEXT field cannot be indexed. It is a bummer since now I had to revert some stuff I did to support SQLite better.

Now there are tests using MySQL. Got them running locally but it took forever because between Python, SQLAlchemy, and commcare-export there are enough layers trying to "just work" that it "just doesn't" :-)

Don't let the apparent simplicity of the results fool you...