Python bindings for DiscreteGlobalBasisFunction use DefaultNodeToRangeMap

The Python-bindings for DiscreteGlobalBasisFunction use DefaultNodeToRangeMap. While this sounds natural, this class is no longer the default on the C++ side for a very long time and has been replaced by HierarchicalNodeToRangeMap. For consistency the same should probably be done in the Python-bindings, too.

Providing a patch should be easy, but I do not use the bindings myself. And I'm not aware if there's maybe a good reason why DefaultNodeToRangeMap is used.