Added unit test for jar.actions property setting

With regards to gradle-2.0 support #16 first I'd like to add an integTest for the jar.actions() setting.  In existing plugin the actions = [new BundleGenerator()] does correctly reset the actions list from 3 built-in actions to just the one bundleGenerator action as shown in this spec.

This integration test is in preparation for trying to work on gradle-2.0 support.