Reworking docs.
Adds qemu-img to list of required Red Hat packages

We need this to provide qemu-nbd.
Add qemu-utils for Debian/Ubuntu.

We need this for qemu-nbd.
Merge pull request #33 from pleia2/master

Remove restart of libvirt-bin from notes.md
Merge pull request #34 from dprince/install-deps-qemu-img

Adds qemu-img/qemu-utils to list of required packages.
More doc improvements.
Update architecture section.
Finish review of README.md.
Add squid cache instructions

Add steps to enable squid cache proxy to speed up image build times.
Merge pull request #36 from jogo/squid

Add squid cache instructions
First pass overhaul of devtest.md.
Stop installing tools globally.
Update d-i-c invocation to modern usage.
Group base image creation and loading together.
Remove dead reference to /e/n/i.
More tweaks.
Use symlinks rather than activating the venv.
Fix node registration - single entry works, but rate limited.
Document why we fiddle with authorized_keys.
Use flavor name, not number.