Added support for othernet lookups via the [domain:<name>] sections in the

sbbsecho.ini file.
The command-line can now support an optional network-name or zone
followed by an optional echolist-URL.
For zones 1 and 21, the echolist URLs have hard-coded defaults that are
(at least currently) valid. If anyone has the other URLs for the EchoLists of
other FidoNet zones or Othernets, please let me know. The URLs must be
an http or https link to an EchoList in backbone.na format.