1. Added msg command to allow the changing of To, From, Subject and so on the

messages. This seems particularly important just now as a whole raft of G3's
seem to be putting out non private bulls to callsigns.
2. While I am at set messages to TO fields that appear to be users to private
if they have been sent as bulls.
3. Add DISTROs, if a callsign field appears in /spider/msg/distro in upper
use that as a list of callsigns to send further. Note this is potentially
recursive as callsigns in a distro can be distros.