Allow cross-site ajax with CORS.

Only allows un-credentialed (as in, no cookies or basic auth), no custom headers, and get (no post, put, delete, etc) requests.

lib/apiaction.php

@@ -102,6 +102,7 @@ class ApiAction extends Action
 
     function handle($args)
     {
+        header('Access-Control-Allow-Origin: *');
         parent::handle($args);
     }