wumpus-basic

Copperbox revision 1700.

I've updated the Path example.

One thing I hadn't realized is that the new drawing monad draws from the background to the foreground for the Z-order. This is the other way round from how things used to work, and I'll have to consider which way is the most 'natural' - especially when Wumpus-Core draws in 'list-order'.

List order is where the front of a list of Prims is drawn on top in the Z-order.