Server-side colors and ISO Contours

* Support for image_rgb output from AR (supports for sever-side coloring, including HD alpha)
* Support for poly_line output from AR (supports ISO Contours)
* Tests (in the spirt of PR905)
mmm... I don't like to much... unittests has to be self-contained... what about writing a monolithic test? See here: http://stackoverflow.com/a/5387956/2785603