[Lib] add OpenDefaultApp event model in Solutions (#2349)

* add OpenDefaultApp event model

* add access modifier

* add map and music uri

* rename MapUri to MapsUri

Author: KayMKM

lib/csharp/microsoft.bot.builder.solutions/microsoft.bot.builder.solutions/Models/OpenDefaultApp.cs

@@ -0,0 +1,16 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+namespace Microsoft.Bot.Builder.Solutions.Models
+{
+    public class OpenDefaultApp
+    {
+        public string MeetingUri { get; set; }
+
+        public string TelephoneUri { get; set; }
+
+        public string MapsUri { get; set; }
+
+        public string MusicUri { get; set; }
+    }
+}