pybind11 bindings: fix image casting in Windows, 64-bit

Closes #731 (closed)

When we cast numpy arrays from python to cpp we did reinterpret_cast<const unsigned long *>(arr.shape()). This fails in Windows x64, due to Py_ssize_t in Windows is long long, so when cast to simple long, then first byte goes to dim_y and second goes to dim_x and it always is 0.

Fixed