Core model transformers test with 7.1.3

Also make the core model transformers tests test against 7.1.3.Final (as well as 7.1.2.Final which was already configured)

I raninto PermGen issues when running these tests with both 7.1.2 and 7.1.3 enabled, so I changed the forkMode from 'once' to 'always'. Perhaps it would have been better to increase the PermGen via command line parameters?