Add option to remove autogenerated firewall rules

[rm4foe0r]

I'm suspecting that opnsense autogenerated rules cause my routing to fail. It should be possible for the user to opt-out of these rules.

UPDATE: issue turned out to be unrelated to firewall rules, nonetheless if I could have easily turn them off I would have quickly recognized that they are irrelevant to the issue instead of wasting a day fiddling with firewall rules (especially when you are new to opnonsense)