Merge pull request #72 from ryanpetrello/linux

Move from `ifconfig` to `ip` for managing interfaces and addresses.
dhcp is only needed for building, then it should be removed
Merge pull request #74 from jordant/linux

dhcp is only needed for building, then it should be removed
Akanda requires bird6 >= 1.3.10. When building Debian Wheezy images we need to
install bird/bird6 from backports.
Merge pull request #75 from jordant/linux

Akanda requires bird6 >= 1.3.10. Setup backports for wheezy
Merge pull request #73 from ryanpetrello/linux

Convert route management from BSD `route` to Linux `/sbin/ip`
Add iptables/iptables-persistent to installed packages
Merge pull request #76 from jordant/linux

Add iptables/iptables-persistent to installed packages
Implement a Linux firewall with iptables and ip6tables.