[Forward-port of 39373ffa72d91ee02e451e307420f9d55352f1b8] Added SchemeHandlerResponse.StatusCode property.
Added SchemeHandlerResponse.RedirectUrl.
Added SchemeHandlerResponse.ContentLength.
SchemeHandlerWrapper bug fix: Must return false from ReadResponse when response is complete.
Added SchemeHandlerResponse.CloseStream, to have SchemeHandlerWrapper close the response stream once it has read all data.