First commit fixes TOC item highlighting and expanding for current page section.
Second commit puts website JavaScript code in a separate file. This reduces the size of the HTML files, sharing the JavaScript code. Also has some other small improvements/fixes.
Note that this fixes the TOC highlighting and expanding for TOC items that are sections on pages, rather than full pages. It does not yet fix the TOC for virtual TOC items, items that exist only in the TOC and are not pages or sections on pages. Fixing that is for a next merge request.
