Improve clarity of what `rights` applies to

[azaroth42]

Although improved in 3.0, the rights property description still has some issues.

• "resource" should be made more explicit as both IIIF resources and Content resources -- the representation that can be retrieved from the id of the resource that has the rights property.
• Remove the note about it being "informative". The intent (IIRC) was to avoid implying that the client needed to enforce the license, only display it.
• Clarify that JSON objects within the document can have different rights (annotation with different rights to the manifest) and how the inheritance works.

Note -- to be determined how rights are calculated with mixed content and iiif resources, such as:

{
  "type": "Manifest",
  "rights": "cc0",
  "provider": [{
    "type": "Agent",
    "logo": {
      "id": "foo.png",
      "type": "Image",
      "rights": "cc-by",
      "service": {
        "id": "https://example.org/iiif/logo",
        "type": "ImageService3",
        "label": {"en": ["Some Text Here"]}
    }
  }]
}

What rights govern the text "Some Text Here"? cc-by inherited from the Image, or cc0 inherited from the Manifest? Similarly, you can dereference the service to get pixels ... are those pixels cc-by or cc0?

Thanks to @zimeon @tomcramer at the IIIF Conference for bringing up the issue