Make WpkgMessageResponse serializable

WpkgInstaller/WpkgMessageResponse.cs

-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+using System.Runtime.Serialization;
 
 namespace WpkgInstaller
 {
+    [DataContract]
     public class WpkgMessageResponse
     {
+        [DataMember]
         public string Message { get; set; }
 
+        public WpkgMessageResponse()
+        {
+
+        }
         public WpkgMessageResponse(string msg)
         {
             Message = msg;