This adds custom CSS classes and a widget to show/hide various parts
of the docs. By default, we show exported interfaces only. The user
can also select "public" (all public interfaces, even those not
exported), and "everything" (even private members).
Issue #1259
Change-Id: Iff8f4d84658a3d19ad8f2f979ab37b256393589f
Joey Parrish