wumpus-basic

Copperbox revision 2188.

The dichotomy between relative and absolute units has larger consequences for Wumpus-Drawing than I realized, so I'm extending the query and drawing primitive modules in Wumpus-Basic to include functions for both units where necessary.

Because absolute units can implement the CtxSize class by ignoring the scaling factor, I initially imagined that higher-level objects could all just use CtxSize. However, this doesn't work for shapes as CtxSize doesn't work with affine transformations nicely. Also Trace Drawings seem to make more sense when limited to absolute units.