Sets the type of the tool. Allows the icon to be changed.
@param {String} type The new type. See the {@link #type} config.
@return {Ext.panel.Tool} this
function(type) {
        var me = this,
            oldType = me.type;

        me.type = type;
        if (me.rendered) {
            if (oldType) {
                me.toolEl.removeCls(me.baseCls + '-' + oldType);
            }
            me.toolEl.addCls(me.baseCls + '-' + type);
        } else {
            me.renderData.type = type;
        }
        return me;
    }