-Added IgnoreSerializableInterface to DefaultContractResolver

-Changed serializing ISerializable types under partial trust to error to fix security issue
-Fixed LinqBridge collision error in .NET 2.0 by moving types to a different namespace
-Fixed JObject.Keys error when object has no items

Src/Newtonsoft.Json.Tests/TestObjects/CircularReferenceWithIdClass.cs

@@ -23,11 +23,6 @@
 // OTHER DEALINGS IN THE SOFTWARE.
 #endregion
 
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-
 namespace Newtonsoft.Json.Tests.TestObjects
 {
   [JsonObject(Id = "MyExplicitId")]