Because the AS-client (and RqP) relationship is now covered entirely by the definition of the UMA grant, we have removed the last vestigial discussion of client credentials with the rationale that OAuth covers everything you need to know about client identity/credentials/authentication/types.

If you think we need to add any language related to this back to Core, speak now. Otherwise, I'll plan to close this issue with no further action by Monday, February 20.