Override dev/device parameter with the query string (bug 1060062)

https://bugzilla.mozilla.org/show_bug.cgi?id=1060062

This will allow /discovery to execute a search for desktop apps only while not affecting anything else (since the UX to allow the user to change how their searches are filtered is still in flux)
it feels weird that this is hardcoded to say 1. where do we update this to say "20-40" when the "More" button is pressed? I just found this: https://github.com/mozilla/fireplace/blob/master/src/media/js/views/search.js#L172