Wumpus

Copperbox revision 834.

I've chosen the polygon-with-points implementation of pictures as the best version of the current round, so I've deleted the others. As this representation carries around affine frames to model displacement of one picture within a composite picture, it can also use the affine frames for transformations - i.e. transform the frame rather than the points within it. One of the examples uses this to rotate a line of squares.