introduce checks which verify that Dockerfile doesn't contain labels which OSBS sets

[TomasTomecek]

• new class to check that a label is NOT present
• release, architecture labels
• a bunch of other labels from https://github.com/projectatomic/ContainerApplicationGenericLabels/blob/master/vendor/redhat/labels.md

This is a low-prio RFE, mainly added here just to track the problem.

[lachmanfrantisek]

new class to check that a label is NOT present

This is already done -- you should only set required = False.

It should be something like this:

      "names": [
        "one",
        "two"
      ],
      "required": false,
      "message": "This label is automatically set by OSBS, do not set them in the Dockerfile.",
      "additional_tags": [
        "required",
         "osbs"
      ],
      "usable_targets": [
        "dockerfile"
      ]

[TomasTomecek]

But still, we would have to create a new check (just tried this out).

Actually required confuses me a bit; probably should_be_present would make more sense.