Add deb_repos.rake, which sets up debian repos for us

This commit adds the automatic creation of debian repositories for the jenkins
build artifacts on the distribution server under the standard location
/opt/jenkins-builds/$project/$sha/repos/deb" where $sha is the git commit sha
of HEAD. With this commit creating the repositories also automatically creates
apt source config files for each packaged distribution, for use later in
acceptance testing, etc.
Add jenkins ship to PE ship
Add repo creation to ship task by default
Split deb repos out into their own task