Enhance: additional table sort modes for small sites

The 'table' mode sorts list names by number of recent messages.

It would make more sense to sort alphabetically by list name within domain name or by list name

I'm not sure why anyone would want to sort by message count as that may cause the order to change from day to day, but for backwards compatibility the new sort orders could be given new names.

Start by locating the implementation of the 'table' mode and its current message-count sorting behavior. Compare the requested alphabetical ordering within domain name and by list name with the existing mode, then verify that the current sort remains available for backwards compatibility and that the new modes produce stable ordering.

Written by the indexing model from the issue text.