- a rework of doc layout and nav:

- a rework of doc layout and nav:
  - reduce the real estate for the top nav; move the search box
    into the top yellow box, close in space
  - use a new CSS/js approach such that the top toolbar freezes from
    scrolling at the top of the page.  The left nav scrolls independently
    of the content pane so that the local contents remain visible regardless
    of scrolling.   this approach is disabled on mobile where the dual scrollbars
    may be cumbersome (overall the site is not well designed for mobile).