Assume creation of attachment dirs

Amendment to 01645a4

* lisp/gnorb-org.el (gnorb-org-attachment-list): There was a reason I
  was using the t argument to org-attach-dir.
Return links in the order which they were found

* lisp/gnorb-utils.el (gnorb-scan-links): It could be useful to have
  them ordered properly.
Fix logic of finding links to reply to

* lisp/gnorb-org.el (gnorb-org-extract-mail-tracking): Behavior was not
  matched to the docstring, this should do it.