Advise curators to respect rights reservations for attachments

[jar398]

At the point where an attachment is uploaded, it would be nice if the curator saw a little request saying that if the document is published with a copyright notice, and there is no license permitting copies to be made, then the document should not be uploaded.

(I.e. if there's no notice, OR there is something similar to a CC license, that's fine.)

(Strictly speaking no notice is slightly risky, but following BHL's lead, we are taking that risk.)