Add org.opencontainers.image.* labels to Dockerfiles

[marccarre]

Why? What?

• This should ultimately help for image-to-code back references.
• org.label-schema.* labels are now deprecated, in favour of org.opencontainers.image.* labels.
  See also: https://github.com/opencontainers/image-spec/blob/master/annotations.md#back-compatibility-with-label-schema
• MAINTAINER is deprecated, in favour of the maintainer label.
• Git revision is now injected at docker build time.

Testing:

$ docker inspect quay.io/weaveworks/launcher-agent
[
    {
        [...]
        "ContainerConfig": {
            [...]
            "Labels": {
                "maintainer": "Weaveworks <[email protected]>",
                "org.opencontainers.image.revision": "dbd70c8482ef23d11f434c6b7e7fde9f7c7b3a62",
                "org.opencontainers.image.source": "https://github.com/weaveworks/launcher",
                "org.opencontainers.image.title": "launcher-agent",
                "org.opencontainers.image.vendor": "Weaveworks"
            }
[...]

$ docker inspect quay.io/weaveworks/launcher-service
[
    {
        [...]
        "ContainerConfig": {
            [...]
            "Labels": {
                "maintainer": "Weaveworks <[email protected]>",
                "org.opencontainers.image.revision": "dbd70c8482ef23d11f434c6b7e7fde9f7c7b3a62",
                "org.opencontainers.image.source": "https://github.com/weaveworks/launcher",
                "org.opencontainers.image.title": "launcher-service",
                "org.opencontainers.image.vendor": "Weaveworks"
            }
[...]