* Replace boost::python with pybind11

* Replace add_python_module with pybind11_add_module

* Fix clang error on type-dependent expression

Can either be a list of full_object_detections or a single
full_object_detection. I couldn't get the vector type to work
for full_object_detection due to a template error.

Also, move the vectorize template into its own header to
stop having to declare it again in vector.