o Better 'dependency' formulation in Makefile.
o Add concept of expiry of codes without a contact info.
  Without contact info, it is not possible to find the 'right'
  line to remove in CSV in case the token is lost or stolen -
  people usually don't remember the 7 bytes ID stored on the
  RFID :)
  Also, similar if revocation is needed - thus even if we don't
  know the ID of the person in question, their token will
  expire.