Update documentation for 'ipfw' backend

[Douglas Thrift]

Apparently version 1.6.2 of sshguard changed how it works with IPFW to use a table of IP addresses instead of creating individual rules. However, it does not automatically set up a rule that uses this table. It would be helpful if there were some example of setting up this rule.

[Kevin Zheng]

Thanks for poking me on the issue. I'm still thinking about how I should collect all the documentation in one place. Would you prefer examples to be in the man pages, the website, or some sort of HTML handbook (or something else)?

[Douglas Thrift]

I think the website makes a lot of sense. It is where I was looking first to figure out why I wasn't seeing any firewall rules after a recent reboot. It is probably also nice to have some information in the man page as well, but the current man page points to the website and that's okay.

[Kevin Zheng]

Fixed, thanks! The new documentation is available at: http://www.sshguard.net/docs/setup/#ipfw