moved code to NPhelper.h
(#486)
Revert "moved code to NPhelper.h"

This reverts commit d79c97f5ee253cf70c46e31b8d40ccfebae9291d.
copied all over from Boost.Numpy dtype.cpp
(#486)
changed some namepsaces
(#486)
added newline at end of file
(#486)
renamed the file to be a bit more descriptive
(#486)