Add export from nsi service

Hcs.TestApp/ClientDemo/NsiDemo.cs

@@ -5,13 +5,13 @@ namespace Hcs.ClientDemo
 {
     public class NsiDemo
     {
-        public static void DemoExportNsiItem(HcsClient client)
+        public static void DemoExportNsiItem51(HcsClient client)
         {
             var result = client.Nsi.GetNsiItem(51).Result;
             Console.WriteLine($"Результат операции:\r\n");
             foreach (var obj in result)
             {
-                Console.WriteLine(obj?.ToString());
+                Console.WriteLine(obj.ToJSON());
             }
         }
     }

Hcs.TestApp/ClientDemo/Program.cs

@@ -67,7 +67,7 @@ namespace Hcs.ClientDemo
                 if (false) FileStoreDemo.DemoGetFileLength(client);
                 if (false) FileStoreDemo.DemoGostHash(client);
 
-                if (true) NsiDemo.DemoExportNsiItem(client);
+                if (true) NsiDemo.DemoExportNsiItem51(client);
             }
             catch (Exception ex)
             {