New Image Surface data access and Filter Primatives

To support more color channels, and greater flexibility in our rendering engine, this additional code implements a new API for accessing pixel data in a cairo surface and expands it's capabilities so that they can work with floating point pixel data as well as CMYKA (5 channel) interpolations.

This code by itself is tested as a stand alone component with separate unit tests. Integration into Inkscape's rendering engine will happen in a different commit and merge request.