update to latest ubuntu 12.04.3
add docker gpg key to avoid package warning
add docker group
add virtualbox builder
update kernel only on aws, as 12.04.3 has 3.8.0-29
enable memory and swap cgroup
Australian-ise.
No need for a "vagrant" user on EC2.
Use the AU Ubuntu mirror.
Merge remote-tracking branch 'justone/docker-inst-updates'
DRY up sudo.