Going green: allow to use bbox param, along lon, lat, and zoom

The `bbox` param was removed from the base controller, the rest kept
working as they are declared in the base, but it's better to declare
them here as well.

Fixes #735.

lib/cartodb/controllers/named_maps.js

@@ -32,7 +32,8 @@ NamedMapsController.prototype.register = function(app) {
         this.tile.bind(this));
 
     app.get(app.base_url_mapconfig +
-        '/static/named/:template_id/:width/:height.:format', cors(), userMiddleware, allowQueryParams(['layer']),
+        '/static/named/:template_id/:width/:height.:format', cors(), userMiddleware,
+        allowQueryParams(['layer', 'zoom', 'lon', 'lat', 'bbox']),
         this.staticMap.bind(this));
 };