wumpus-basic

Copperbox revision 1583.

I've replaced the DrawingCtxMonad and TraceMonad with a new DrawingMonad. With the AGraphic type monadic drawing needs both tracing (writer) and drawing context (reader), so having one monad to do both is more efficient. I've made trace type specific to Graphic which is a Hughes list so supports efficient append.

The ConsDrawing monad has also been removed.