interpolation.h: changed dlib::array<image_type> to image_array_type

--HG--
extra : rebase_source : 3875b192c4c15d82b8106a17020ed53ff922c8ef
Changed python pickling code so it works with Python 3
Changed python cmake scrips to have an option to compile Python 3 libraries.
Made the compile time assert macros use static_assert if it's available.
Set correct include directory for fftw
merged
Made cmake better at finding OpenBLAS installs, in particular, it will
now find them if you install straight from the OpenBLAS source.
Fixed CSS to use class instead of id tags.
Minor changes to cmake scripts to avoid warnings in new version of cmake.
Another minor cmake change to avoid warnings
more cmake changes to avoid cmake warnings
Added pixel_traits definitions that allow you to copy images
into complex valued images using any dlib functions.
Added max_point()
Added min_point()
Added some unit tests
updated docs
Merged and also clarified requires clauses.
Added max cost assignment example program
updated docs
clarified spec