Add classes to history when tree nodes clicked.

        this.control({

            '#treePanelCmp': {

                classclick: Ext.Function.bind(this.loadClass, this)

                // Can't simply assign the loadClass function as event

                // handler, because an extra event options object is

                // appended to the event arguments, which we don't

                // want to give to the loadClass, as this would render

                // the noHistory parameter to true.

                classclick: function(cls) {

                    this.loadClass(cls);

                }

            },

            '#classlist': {