Issue#18: Requesting ARs to perform ONLY reverse address translation

issue#18 raised by Vijay on "section 4: CARD protocol operation":

[Vijay]"lets say, the MN is interested only in reverse address
translation and not in capability information. How does the
MN indicate this to the access router? I think supporting
this is essential."

[marco]I agree to this and solutions could be very different
(set a flag or append appropriate Preferences sub-option[indicate NO ATTRIBUTES], ...).

Maybe a flag is most appropriate for this indication to avoid
superfluous protocol overhead, what do you think?

marco