Stop using low level numpy array interface

[kjmeagher]

In 292eaad, I removed all the compiler warnings but on of them was warning of an issue with numpy API. We include ndarrayobject.h which the first comment in is DON'T INCLUDE THIS DIRECTLY. We should switch to a better python numpy array interface, either pybind11 or boost-numpy I don't know which one is better in this situation.

[kjmeagher]

The interface we access numpy with is obsolete as of numpy 2.0. This means that we will have to restrict numpy to numpy<2 until the python interface is rewritten. The options for which interface to switch to remain the same.