Change the way the rules are flushed/remove from the iptables.

[Haerezis]

All the rules are now added with a custom comment, and we flush/remove the rules by greping and removing the rules with that comment.

We do this do avoid flushing the rules setup by other scripts or configurations.

I've made this commit because the initial version was flushing ufw rules which was bad :s.

[bendikro]

Great stuff. Thanks!