Implement general Fx Open Search for the site

* Upcoming Fx 33 has this on about:newtab... so best to get us in there early... does work with earlier versions too.

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Since we would need to dynamically generate individual user and comments links along with xml source this might not be an option... unless there is a per session creation and destruction of these files... might be too much for the drones though when a ton of users are on the site... Definitely past this pr request.

I could optionally add optional sorting QSP item features but we seem to have some boogs running around with that.

Future dependencies depending on who gets in first **soon** *hint hint* ;) :
* Probably something in #250
* Possibly #135

Retested installation from dev and using with newer search parms on pro already... been using a variant of this and current pr since day one of being on here. :)

See also:
* [Wikipedia OpenSearch](http://en.wikipedia.org/wiki/OpenSearch) - Does have multiple browser support just not as easy to add in other browsers. ;)