This method returns the configuration object for the Desktop object. A derived
class can override this method, call the base version to build the config and
then modify the returned object before returning it.
function () {
        var me = this, cfg = {
            app: me,
            taskbarConfig: me.getTaskbarConfig()
        };

        Ext.apply(cfg, me.desktopConfig);
        return cfg;
    }