Update all the debian and ubuntu images with the newer debootstrap script

This includes running "apt-get update" as the last step of each image, and fixes some problems that were specific to the ubuntu:lucid image.

Finally, I've added more debian images:
- debian:stable, debian:testing, debian:unstable are all tagged to the "release" in /etc/apt/sources.list
- debian:experimental and debian:rc-buggy include the "experimental" repository on top of sid/unstable
Merge pull request #24 from tianon/update-debian-and-ubuntu

Update all the debian and ubuntu images with the newer debootstrap script