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. There are already several separate DB tests so this makes things more consistent. ebean and anorm shouldn't be treated differently from jpa, slick, etc.
* Download sbt so that Play 2.3 can use it.
* 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.
After you rebase onto master, you'll note that all of these now use the IROOT variable, so you'll want to update this to `export SBT_HOME=$IROOT/sbt`