- added test for NCubeManager.getReferencedCubeNames().  In the process, discovered that it was not actually recursing.  Add circular reference test to ensure recursion and to ensure no infinite loops.
- added test to ensure that in the simple case of a->b, that the answer only includes "b".
- fixed a broken test -> if a->b and b->a, then the referenced cube names is [a, b] because although we 'asked' a, b pointed to a, therefore 'a' is also in the list.