Make CORS great again

This fixes CORS to work properly with most 2.5 api endpoints while keeping the JSONP format available.

* [x] return JSONP or JSON with proper CORS headers from API
* [x] Field in Genereal Preferences Form to configure CORS enabled URLs

See #17 for what triggered this refactor. I beleive this should make integrating the APIs on the client side trivial without mandating the use of JSONP.

airtime_mvc/application/controllers/LoginController.php

@@ -24,7 +24,7 @@ class LoginController extends Zend_Controller_Action
         $stationLocale = Application_Model_Preference::GetDefaultLocale();
         
         //Enable AJAX requests from www.airtime.pro for the sign-in process.
-        CORSHelper::enableATProCrossOriginRequests($request, $response);
+        CORSHelper::enableCrossOriginRequests($request, $response);
 
         
         Application_Model_Locale::configureLocalization($request->getcookie('airtime_locale', $stationLocale));