ip(6)tables-multi: unify subcommand handling

I found the subcommand handling and naming done by iptables-multi and
ip6tables-multi very confusing and complicated; this patch
reorganizes the subcommands in a single table, allowing both variants
of them to be used (iptables/main) and also prints a list of the
allowed commands if an unknown command is entered by the user.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
4 files changed