dhcpd: Minimal working Dockerfile

* Build:
  $ docker build -t=dhcpd .

* Run:
  $ docker run dhcpd

* In another shell attach the network bridge with:
  $ sudo ./pipework em1.40 $(docker ps -q | head -n1) 192.168.40.2/24
dhcpd: Tweak config file for all subnets

* Tweak for all subnets
run: Wrapper to launch the containers and bridge

* Create new containers and run them.
* Run pipework on them to bridge them.