Split Play tests / upgrade non-DB tests to Play 2.3

* Split the DB tests out of play-scala and play-scala and into new tests. This means they match the naming for the other DB tests (play-java-jpa, play-scala-slick, etc).
* Update the non-DB tests to Play 2.3.0. We will need to update the DB tests too, but that's a big job that can be done separately. I'm going to ask the community if they can help with updating the DB tests.