Merge lp://staging/~sinzui/juju-release-tools/build-package-from-changes into lp://staging/juju-release-tools

Add a dedicated script that can build binary packages from source packages. It can build on the local host, a remote host, or an ec2 instance.

assemble-public-tools.bash
    * This script only cares about juju-core debs, not the juju-local deb.
    * I kept the readlink code because I felt safer with using it.
make-package-with-tarball.bash
    * Removed knowledge of binary packages
    * Updated the args to accept -t to explicitly state we want testing packages
      Instead of implying the series. We always want to be clear about the series under test.
    * The leading ":" in getops was bogus; I wish getopts had told me that.
make-source-packages.bash
    * Renamed the file because I don't intend to teach it uploading any more.
    * Added the getopts -t (and removed the same bogus ":". It is passed to make-package-with-tarball.bash
build-package-with-dsc.bash
    * The new script that makes packages for the correct series and arch.
      It accept localhost, a remote host or ec2 information: eg
      build-package-with-dsc.bash localhost '' $dsc
      build-package-with-dsc.bash ubuntu@stilson-07 "$PPC_SSH_OPTIONS" $dsc
      build-package-with-dsc.bash m1.medium ami-81dee0e8 $dsc
    * I think the create_instance() function can be placed in a common lib or copied to run-unit-tests*
    * install_build_deps() evals a string of commands because I didn't want to write the commands twice...
      ...localhost needs an interactive shell since sudo is interactive
    * The [eval "set -- $ssh_options"] hack to place the ssh options in "$@" is used because
      it is the only way I found to let jenkins do complicated ssh maneuvers.
    * Is it maintainable?