[Therion] wall coloring

this is for kevin's request. not a solution, just a proof of concept ... (without important details) to color the wall you can re-define l_wall with a code metapost in the layout, passing the R,G,B values after the path. next set the layout color map-fg altitude to have the altitude stored in the scraps. (see sample thconfig) finally have therion write the parent scrap R, G, and B, after the wall path, and use 0,0,0 when it writes the scrap. (see howto) i'm attaching also the output cave.pdf. ... i'm not sure how useful wall-coloring may be ... anyways i leave up to therion developers whether to add a layout option to color wall, map-fg, or both. cheers, marco