Prune obsolete css

During the redesign I whacked the section that this referred to.
Prune redesign directory

This is where @nicksergeant stored his work during the markup mockup
phase of the redesign (#516). We're done, it's done.
Rationalize colors; #610

This cleans up places where we were using one-off colors. Now all colors
in the css fall under three classes:

 - color variables defined at the top, like $brown
 - simple names (white) or three-digit (#000) colors
 - highlight, a one-off