luci-app-openairview: rename function action_stations_json -> action_json_stations
luci-app-openairview: add /usr/lib/lua/luci/controller/spectral_scan.lua
luci-app-openairview: add /usr/lib/lua/luci/view/openairview/spectral_scan.htm
luci-app-openairview: add openairview/json/spectral_scan handler to controller
luci-app-openairview: integrate spectral_scan.lua into openairview.lua
trivial aestethic fixes; make stations graph width 100% instead of 760px
rename adhoc interfaces, now they include 'wlan' prefix (ie. wlanXah) to avoid breaking luci heuristics
better integration of stations plot into luci:

 * include cbi-tabmenu
 * allow passing device as a parameter to action_json_stations
 * use XHR instead of $.ajax
add a 'Polling delay' control widget to dinamically adjust XHR.get interval
use plain MAC as identifier, if station couldn't be resolved through bat-hosts
crappy workaround for broken CSS, place stations legend on a separate <div>
nest action_json_spectral_scan inside /admin/ to avoid unauthenticated DoS
Merge branch 'luci-app-openairview' into develop

Spectral Scan is fully integrated into LuCI MVC,
and Stations plot now correctly supports passing interface as an argument
among other improvements