Install most packages needed by AppScale

This will yield better cache hits by allowing more of the installation
to be reused when building the Docker image.
Updated AppScale Tools version

Stick to 1.12.0 as it's what the docker branch is using.
Updated sources.list change

Make this more idempotent so that the sources.list file doesn't get
polluted with redundant lines.
Added universe/multiverse repos to sources.list
Added gemrc

Do not install documentation.  This slows down builds and docs are not
needed in production.
Broke down adding files from appscale repo

For cache purposes only add the files needed to install the AppScale
platform.  That way if any runtime-specific files change it will not
bust the image build cache.
Bumped file version