[askrover_styling_prune_css] Remove signin links from header.
[askrover_styling_prune_css] Remove copied css in favor of single override file.
[askrover_styling_prune_css] Move css out of new_design directory.
[askrover_styling_prune_css] Remove copied new_design media.
[askrover_styling_prune_css] Add import of overridden style to html header.