Updating play2-java-jpa

@hamiltont @richdougherty I've updated the Play JPA project.
Travis validation build seems ok: https://travis-ci.org/donovanmuller/FrameworkBenchmarks/builds/33564344

Have tried to make the changes consistent with those made in [play2-java-ebean](TechEmpower/FrameworkBenchmarks/tree/master/frameworks/Java/play2-java/play2-java-ebean)