When building or committing an image in OCI format, default to setting
the org.opencontainers.image.created annotation to the value used in the
image's config blob for the image's creation date. The behavior can be
controlled using the new --created-annotation flag.
Add --annotation and --unsetannotation flags to `buildah commit` which
mimic the same flags for `buildah build`.
Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>
