libcutter/Cricut SVG Support

My latest update to libcutter implements basic SVG support.

There are a few things missing, but ovals, arcs, circles, rectangles, and Bezier all work. In fact, everything I've drawn in InkScape has worked so far. The SVG interpreter is based on the early libsvg. Sadly, libsvg was merged into Cairo, and is now the libsvg-cairo. libsvg-cairo is much less sharable with other projects than the old libsvg.