Add "none" client authentication method

[Vladimir Dzhuvinov]

From the WG list:

---

From:
Mike Jones [e-mail] (Add as Preferred Sender)
Date: Thu, Nov 28, 2013 2:17 am To: "[e-mail]" [e-mail]

Justin proposed that we add the following to the set of Client Authentication identifiers:

none

The Client does not authenticate itself at the Token Endpoint, either because it uses only the Implicit Flow (and so does not use the Token Endpoint) or because it is a Public Client with no Client Secret or other authentication mechanism.

[Vladimir Dzhuvinov]

Done in commit 3233a18.