iptables actions: add table and rulenum options

[me-vlad]

• add table option (defaults to "filter") to be able inserting Fail2Ban rules e.g. to the raw table for better performance reasons
• add comment with common values of the chain option (INPUT, PREROUTING)
• add rulenum option (defaults to 1) to use with iptables insert for cases where user wants to prepend Fail2Ban rules with own iptables rules (e.g. hardcoded allowlist rules maintained outside of Fail2Ban) Default behavior of the iptables* actions remains unchanged - Fail2Ban rules should be added at the head of the INPUT chain of the filter table.