This removes all the SVG sources, parsing, and marked-layer colorizing, the PNG binaries in the distribution, and the dependence of DrRacket on `slideshow/pict'.
Icons are now produced by drawing on a bitmap-dc%, inferring or building a z map, choosing a material, and sending these to a two-pass ray tracer. This is for the most part hidden behind an API consisting of functions from colors and optional sizes and materials to `bitmap%'s.
Contracts and documentation forthcoming.
