adds a new uci firewall - iptbales and netfilter packages need to be rewrapped when we switch to this firewall as default - there are some examples in the file /etc/config/firewall - iptables-save/restore are still missing - hotplug takes care of adding/removing netdevs during runtime - misisng features ? wishes ? let me know ...

SVN-Revision: 12089

prepare for moving part of the firewall to hotplug. created new chains {input,forwarding,prerouting}_wan for wan port forwardings and updated the examples. syntax of /etc/config/firewall unchanged and old firewall.user files are still compatible

SVN-Revision: 5878