Wumpus

Copperbox revision 831.

I've added rotation to the current toy picture type. It's not satisfactory, for affine transformations I'd be happier working on points rather than vectors - all the literature I've read on affine spaces uses points to illustrate the affine transformations rather than vectors.

I've also worked through a version of the (vector) polygon and picture types that use displacement from some common origin rather than displacement from the last point in the vertex list. Neither seem to make the affine transformations more tangible.