/**
  \example trigger.cpp 

  Many non-SFB devices actually 'speak SFB packets' in the sense of
  producing reasonably short, newline-terminated, sequences of
  (printable) ASCII characters.  But they're not true SFB's, so we
  can't talk to them as if they were -- because for one thing, they
  don't know how to perform SFB baud rate negotiation.

  A GPS unit that produces 'NMEA sentences', for example, might be
  such a device -- an NMEA 0183 sentence begins with a '$', contains
  'normal' ASCII characters, and ends with a carriage return and a
  newline.

  In such a case, assuming a baud rate has been agreed upon in
  advance, conscious packet handling on some specified face can be
  used to acquire packets from the device.  Given such a packet,
  though, often what is desired is to have the system 'react' to the
  packet \e as \e if it had been received via full packet handling.

  The SFBReactor::trigger() method, demonstrated in this sketch as
  'Body.trigger()', provides a way to pass a packet back to the core
  software, saying in effect: "Trigger the appropriate reflex for this
  packet, assuming it arrived from this face."

 */
