Work on and close issue #522 ...

Do not put ops into the external named file when ops does not have a
routable IP address.

And very much related, when ops does not have a routable IP, we do not
want it to be the MX for the testbed, since email cannot be replied to.

Added a new MAILERHOST config variable, when set to "boss", boss becomes
the mailer instead of ops. The lists are maintained on boss, the MX
record is set to boss in the named file, the sendmail install script is
run on boss, yada yada.

Included is a bit of ELABINELAB cleanup; pass the creator email into
configure via a new config variable, and initialize the email lists
to the creator, instead of doing this in three different places in
rc.mkelab after the install.