Return error type AUTHENTICATION for FacebookOAuthException.

AUTHENTICATION is returned instead of PARTNER_SERVICE_FAILURE for RestFB OAuth Exceptions.

````json
{ "error" : 
    { "message" : "Received Facebook error response of type OAuthException: Error validating access token: Session has expired at unix time 1371898800. The current unix time is 1372031646.",
      "stackTrace" : "com.restfb.exception.FacebookOAuthException:..",
      "type" : "AUTHENTICATION"
    } 
}
````