Add docker base image metadata
    
    Currently we don't produce a docker base image that can be used with
    OSBS or via the 'atomic run' command without modification. This
    fixes that and will allow for an automated import of the base images
    into the Fedora Container Registry
    
    Switch from docker to container namespace
    
    Fedora Atomic WG has decided to move from the "docker" namespace to
    the "container" namespace for the sake of making it more generic in
    order to target all OCI Compliant container runtimes instead of
    a specific implementation. This update changes what is necessary for
    to the base image metadata.
    
    Signed-off-by: Adam Miller <maxamillion@fedoraproject.org>