Fix public key token serialization issue

src/lib/Microsoft.Fx.Portability/DataExtensions.cs

@@ -26,6 +26,7 @@ public static class DataExtensions
                 new JsonMultiDictionaryConverter<MemberInfo, AssemblyInfo>(),
                 new JsonToStringConverter<FrameworkName>(s => new FrameworkName(s)),
                 new JsonToStringConverter<Version>(s => new Version(s)),
+                new JsonPublicKeyTokenConverter(),
             }
         };
 

src/lib/Microsoft.Fx.Portability/DocumentationLinks.cs

@@ -9,6 +9,6 @@ public static class DocumentationLinks
     {
         public static readonly Uri PrivacyPolicy = new Uri("https://privacy.microsoft.com/en-us/privacystatement");
 
-        public static readonly Uri About = new Uri("https://go.microsoft.com/fwlink/?LinkId=506955");
+        public static readonly Uri About = new Uri("https://aka.ms/dotnet-portabilityanalyzer");
     }
 }

src/lib/Microsoft.Fx.Portability/Utils/JsonConverters/JsonPublicKeyTokenConverter.cs

@@ -0,0 +1,29 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Microsoft.Fx.Portability.ObjectModel;
+using Newtonsoft.Json;
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Security.Cryptography.X509Certificates;
+using System.Text;
+
+namespace Microsoft.Fx.Portability.Utils.JsonConverters
+{
+    internal class JsonPublicKeyTokenConverter : JsonConverter<PublicKeyToken>
+    {
+        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+        {
+            string publicKeyTokenString = serializer
+                .Deserialize<string>(reader);
+            return PublicKeyToken.Parse(publicKeyTokenString);
+        }
+
+        public override void WriteJson(JsonWriter writer, object obj, JsonSerializer serializer)
+        {
+            PublicKeyToken pkToken = (PublicKeyToken)obj;
+            serializer.Serialize(writer, pkToken.ToString());
+        }
+    }
+}