Revise the control string generation in action responses

[fcastilloes]

Currently, to activate the control bytes to send in an action response, it was checked if any calls, transactions, files or body exists in the transport. That is not entirely correct, because the check is that any of those has been added in that action.

So the solution should be a new ControlString object to assign to the Transport. If the action adds any of those controlled items, a flag should be set in the object. When the response is being prepared, a method ControlString->get() should be called to generate the actual string.