support ubuntu12

[ssst0n3]

to fix #55

What this commit did:

1. mkfs.ext4 -O ^has_journal,^metadata_csum
2. restore initctl
3. setup ttyS0
4. remove packages ubuntu12 does not support

Testcase:

$ cat Dockerfile                                                                                                                                     
FROM ubuntu:12.04

# apt sources
RUN sed -i 's/archive/old-releases/g' /etc/apt/sources.list

$ docker run --rm -it -v /var/run/docker.sock:/var/run/docker.sock --privileged -v $(pwd):/d2vm -w /d2vm ssst0n3/d2vm:v0.2.1-dev build -f Dockerfile . -v

$ cp disk0.qcow2 vm.qcow2
$ qemu-system-x86_64 -hda vm.qcow2 --enable-kvm -nographic
...
Ubuntu 12.04.5 LTS localhost.localdomain ttyS0

localhost login: 

[ssst0n3]

see #58