Add bodhi-skopeo-lite - a skopeo-workalike with manifest list support

In order to support copying multi-arch containers and Flatpaks, we need
to be able to copy manifest lists and OCI image indexes from registry to
registry. Work is underway to add such support to skopeo
(containers/image#400), but as a temporary workaround
add 'bodhi-skopeo-lite', which implements the subset of 'skopeo copy' we need,
but with manifest list/image index support. Use of this needs to be specifically
configured.

Signed-off-by: Owen W. Taylor <[email protected]>