Wumpus

Copperbox revision 854.

First round of changes towards adding graphics state operations (colour change, line width change etc.) to the revised Wumpus.

The original Wumpus had a rather confused evaluation mechanism that attempted, via a reader monad, to track differences between the local graphics state and the world state during rendering and only transmit changes to PostScript. The new version has changed the environment data types of the original into 'update commands' that will instead be part of the syntax of pictures, paths and labels.