wumpus-basic

Copperbox revision 2572.

I've added a new module Trail for what were previously path schemes or point schemes.

I thought of the name Trail this morning on the lines of breadcrumb trails and the Slint song and it seemed to fit better than path scheme (or PrePath, PathPlan...). Coincidentally, I discovered later that Diagrams has a module Trail for Path like functionality - I follow the Diagrams mailing list, but don't know the library well as I haven't been able to build it on Windows.