Support loading and saving tarballs with more than one image.
Add a new `/libpod/images/export` endpoint to the rest API to
allow for exporting/saving multiple images into an archive.
Note that a non-release version of containers/image is vendored.
A release version must be vendored before cutting a new Podman
release. We force the containers/image version via a replace in
the go.mod file; this way go won't try to match the versions.
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>
Valentin Rothberg
Matthew Heon