templatize u32_pt_t to experiment with usage of i32_pt_t in for feature<-->image space conversion iface
cleanup prior to template-izing u32_box_t
minimal templatization of u32_box_t; add i32_box_t typedef.
typo fix ciel->ceil
add u32 ceil_div() functions
comments and some starting sketchy code for image<-->feature space conversion functions