Adding test application for automated testing

As #50 & #73 note, Scala compatibility is limited in *play-authenticate* currently, but not
entirely absent. Automated testing should improve this situation.

This test application provides a very basic automated testing environment, which implements a UsernamePasswordAuthProvider and associated support classes in Java, and tests controller protection for Java & Scala.

Tests of the Scala controller are written in Scala too.

The main aim is to provide very basic test coverage of core play-authenticate functionality. Hopefully this should serve as a base for full Scala compatibility at some later stage.