removed imy from call to unsharp_mask
add Cython bindings to unsharp_mask and subtract_img
All runs nicely with the Lena, except the highpass result which is dark
high pass works - with py_enhance we can see the rough edges of Lena
Cython binding for subtract_mask and test with a rectangular mask
Merge branch 'image_processing' of https://github.com/alexlib/openptv into image_processing

Conflicts:
	liboptv/src/image_processing.c