Make changes to handle ndarray now using size_t for its array sizes

In the v12_1 release, we're switching to using ndarry as an external dependency, and one change is that it now uses size_t not int for array sizes (in conformity with the C++ STL).

Unfortunately, things like

ndarray::makeVector( shape[0]-1, 1 )

fail to compile (as shape is size_t and 1 is int). The fix is

ndarray::makeVector<size_t>( shape[0]-1, 1 )