Iptables provider and two cookbooks for selecting iptables/ufw

- Adds two new cookbooks for selecting ufw and iptables
- Adds LWRP for iptables and iptables_rule
- Adds some configuration for compatibility (e.g. empty :flush action in ufw provider)

!Attention!
As soon as iptables firewall is enabled, everything is blocked (until you are adding some routes), so be careful!

I might provide some examples as needed.