Support "nonce" OpenID Connect auth request parameter

[iainmcgin]

OpenID Connect Core 1.0, Section 3.1.2.1, "nonce" parameter:

OPTIONAL. String value used to associate a Client session with an ID Token, and to mitigate replay attacks. The value is passed through unmodified from the Authentication Request to the ID Token. Sufficient entropy MUST be present in the nonce values used to prevent attackers from guessing values. For implementation notes, see Section 15.5.2.

Section 3.2.2.1, "Authentication Request" specifies that this parameter is REQUIRED for implicit flow authentication requests (those with response type id_token or id_token token).

[WilliamDenniss]

This has been implemented.