[elbe-devel] Project Repository functionality

[Philipp Arras]

Hi everybody,

I added three commands to ELBE which relate to the Debian repositories inside
every project directory in the initvm:

  - `elbe prjrepo list_packages <build_dir>` lists the available packages
  - `elbe prjrepo download <build_dir>` downloads the Debian repo as tarball
    from the initvm to the host machine.
  - `elbe prjrepo upload <build_dir> <deb/dsc file>` uploads a Debian package
    into the Debian repository of the specified project and updates the
    repository accordingly.

Cheers,
Philipp