Roofing

Adding roof tiles and extending the buildings to arbitrary footprint polygons were not well planned for features from from the beginning but their addition was an excellent excuse to clean up some of the older code.  After some reworking of the code to make them function.  In the grammar 'r' is now a reserved symbol that indicates the grammar to be used for the roof.  In the general section there is a "footprint" line that overrides width by having each side of the polygon listed after.

This results from:

r ty
   y ty
and
footprint 0,0 14,-5 10,0 10,-10 0,-10

The protruding features of the roof  the break plane (cornice and slope) are neatly adjusted at the corners to avoid messy overlap.  Overall the output looks much more like buildings now