Move all code related handling container image over to the new
`libimage` package in containers/common. The new package is an
attempt to consolidate the code across the containers tools under the
github.com/containers umbrella.
The new `libimage` packages provides functionality to perform all kinds
of operations for managing images such as local lookups, pushing,
pulling, listing, removing, etc.
The following packages have been moved over the containers/common:
`manifests` -> `common/image/manifests`
`pkg/manifests` -> `common/pkg/manifests`
`pkg/supplemented` -> `common/pkg/supplemented`
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>