Geometry 2

(In re: this and the one above)
This example seems to have been oriented toward showing the object-oriented goodness of Java, so there is (and even was; I chopped out a lot of stuff) a fair bit of unnecessary engineering in here, e.g. the Icosahedron can take a `radius` argument to set it's size, even though it's never changed **in this example**.
I'll continue to simplify where I can.