Better testing of properties via a test harness

[eeverman]

Currently all property testing is done in the AndHowTest, which is a big overloaded test that uses SimpleParams to test a bunch of interactions.

Instead, it would be nice to isolate a type of property into a group and run just it thru some tests. The harness could configure AndHow in a standard way, using the test class name as the name of a properties file on the class path to load props from.