* Add documentation for -s.

* Add documentation for -s.

* Move the configuaration examples to an EXAMPLES section and model the
  setup of the root image file after the setup instructions given in
  jail(8) (i.e., use 'installworld' and 'distribution' instead of
  cpdup'ing the host system's /). Add some lines for setting up simple
  /etc/fstab and /etc/ttys files.

* Add some references to SEE ALSO.

* Minor mdoc additions/cleanup

TODO: document -I