Session calls undefined method IResponse::removeDuplicateCookies()

`Nette\Http\Session` calls the method `Nette\Http\IResponse::removeDuplicateCookies()`. This method however isn't defined on the interface but only in `Nette\Http\Response`. Therefore Session doesn't work with custom implementations of IResponse.

Is it ok to add the method to the interface or do you think it should be fixed differently?