fw: Optimized IPTraffic and OpenVPN iptables rules.

1) Moved all IPTraffic rules to two chains handling inbound and outbound traffic.
   That will split at least in half the number of rules to traverse for
   all packets.
2) Since the primary WAN Rule will be first in each chain, it should cut down
   rule processing for a typical packet to only two rules instead of 4-6 rules
3) Only generate IPTraffic rules for DualWAN interfaces if it's enabled
4) Moved OpenVPN interface rule after the ESTABLISHED,RELATED rule,
   meaning one less rule for all non-VPN traffic to traverse.