Removed more old and unused JS code and documented some used ones.

* addCommas() & parseIntWH() were/are used by /extensions/wikihow/rcpatrol/rcpatrol.js, but since that's the only caller, that's where the functions in question should reside, not here
* emailLink() / setupEmailLinkForm() / the whole "send this article to a friend" stuff is very hairy and needs lots of love
* wfTemplate() is used only by wikiHow's CommunityDashboard extension (and, technically speaking, their old HTML5Editor extension, which they no longer use, calls it, too), so removed it
* Documented plusone_vote() and added an if() check there because not everyone uses Google Analytics
* scroll_open() was totally unused, so it's gone

Change-Id: I97e099b7e483ec440cc05539e75b203a9f49b36b