ISIS-776: initial implementation
ISIS-776: retroft with applib.InstallableFixture; decouple org.reflections...

dependency by introducing a new ClassDiscoveryService.

Also:
- fixes for todo app's integration tests, to use the ToDoItemsFixtureService rather than ToDoItemFixture directly (ie uses fixture scripts to setup).
- ignored RO TCK test (ISIS-421)
ISIS-550 and ISIS-776: merging
ISIS-550: PostsCollectionRemovedFromEvent implemented. Subscription Tests needed
ISIS-550: fixing unit test.