Added shading to the strata demo which is awesome as well as some simple
particles that roll downhill (just to test the gradient function for
now).

-Peter Mawhorter
Updated the strata prototype to include noise demos for messing with
noise functions. Current default is a Worley-noise-based algorithm for
rock veins.

-Peter Mawhorter
Found that distorting Perlin noise using Worley noise produces a
mountains-like texture and added a noise test for that.

-Peter Mawhorter
Progress towards strata-based world generation, as well as some
restructuring (there's a new module called "math" that has the old
Bezier curve functionality as well as some new mapping functions (which
need to be merged with plant leaf shapes at some point). Also added some
convenience functions in noise.h along with a sped-up version of Worley
noise for when the default flags are used. Finally, added a stub for
representing materials, although that's going to evolve a bit before it
settles down I think.

-Peter Mawhorter