[setup] added a macro 'HAVE_NUMPY', if numpy is importable
[JPJavaEnv] added functions to get/release arrays critical.
[primitive arrays] return a slice via a numpy array, if api is available.
[test/array] use 'assertItemsEqual' to check arrays for equality (assertEqual does not work for numpy arrays)
[primitive arrays] define dummy numpy types in case numpy is not available
Merge pull request #73 from marscher/numpy_arrays

support returning Numpy arrays from primitive array getters