(style) Rewrite the navigation sidebar accordion script (allow subsections, allow multi-section pages, add "expand all")
(style) Refactor nav accordion a bit

Two of those custom events were easy-to-understand one-liners that were only
used once.
(guts) Upgrade jQuery to 1.11.1

Now that I've rewritten the nav sidebar and fixed the bug with the drop-downs,
we're safe to upgrade to the latest 1.x version of jQuery.