majalan-basic

Copperbox revision 2510.

Work on score representations - primarily the Turtle score object (and design variation CtxTurtle). This has an unfortunate name, but essentially it models turtle drawing as sometimes used in Wumpus.

The work so far has unearthed some problematic design ideas with Wumpus, particularly in relation to context handling - CtxTurtle in Majalan can support the local operation of a reader monad whereas the counterparts in Wumpus cannot.