Add Labels to Docker images

[nuest]

Use LABEL in Dockerfiles and give example of using docker inspect to see core metadata.

[nuest]

The spec currently does not need labels to fulfil all requirements. Using tags is more straightforward.

The Label Schema approach made it into the OCI spec, so using labels instead of tags might become more relevant if ERC would use OCI.

Label Schema

• http://label-schema.org/rc1/
• https://github.com/label-schema/label-schema.org
• https://microbadger.com/labelschema
• https://groups.google.com/forum/#!forum/label-schema
• https://medium.com/microscaling-systems/labelling-automated-builds-on-docker-hub-f3d073fb8e1#.770k6qukh
• https://docs.docker.com/docker-cloud/builds/advanced/#override-build-test-or-push-commands

Project Atomic

• http://b4mad.net/datenbrei/container/on-labeling/
• https://github.com/projectatomic/ContainerApplicationGenericLabels/