Portshell crypto trickery

I re-polished some of my old tools and imported them
to github. This time it was psc.

The port-shell crypter (psc) allows you to 'upgrade'
previously unencrypted sessions, no matter whether
its a multi-hop SSH session, a portshell without a tty,
telnet, rlogin or minicom.
It gives you a full pty with end-to-end encryption.

You can also use it as a kind of two-factor authentication
with SSH, if you add psc-remote as shell inside
/etc/passwd or use OpenSSH's ForcedCommand option.