[AppWell] Enable lightboxing immediately on popup

Rather than starting lightboxing only when the mouse enters the
menu, start it when an application filter is set.

Also delete a stale function in WindowClone from previous work.

http://bugzilla.gnome.org/show_bug.cgi?id=594555

js/ui/appDisplay.js

@@ -791,7 +791,7 @@ RunningWellItem.prototype = {
                     id = this.appInfo.get_id();
                 else
                     id = null;
-                Main.overview.setWindowApplicationFilter(id);
+                Main.overview.beginApplicationWindowSelection(id);
             }));
         }