Issue 351: Reimplement OAuth2 - Step 2 (Auth PCL - only data types)

Src/GoogleApis.Auth/GoogleJsonWebSignature.cs

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
 namespace Google.Apis.Auth
 {
 /// <summary>
 /// Google JSON Web Signature as specified in https://developers.google.com/
accounts/docs/OAuth2ServiceAccount.
 /// </summary>
 public class GoogleJsonWebSignature
 {
+// TODO(peleyal): We should provide a way to verify JWS.
+// Take a look at: https://github.com/googleplus/gplus-verifytoken-cshar
p/blob/master/verifytoken.ashx.cs.
+
 /// <summary>
 /// The header as specified in https://developers.google.com/accounts/do
cs/OAuth2ServiceAccount#formingheader.
 /// </summary>
 public class Header : JsonWebSignature.Header
 {
 }
 
 /// <summary>
 /// The payload as specified in·
 /// https://developers.google.com/accounts/docs/OAuth2ServiceAccount#for
mingclaimset.
 /// </summary>
 public class Payload : JsonWebSignature.Payload
 {
 /// <summary>
 /// a space-delimited list of the permissions the application reques
ts or <c>null</c>.
 /// </summary>
 [Newtonsoft.Json.JsonPropertyAttribute("scope")]
 public string Scope { get; set; }
 
 /// <summary>
 /// The email address of the user for which the application is reque
sting delegated access.
 /// </summary>
 [Newtonsoft.Json.JsonPropertyAttribute("prn")]
 public string Prn { get; set; }
 }
 }
 }