Adding service operations for external languages (#918)

* Added service operations for external languages

src/Microsoft.SqlTools.ServiceLayer/LanguageExtensibility/LanguageExtensibilityException.cs

@@ -0,0 +1,27 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+
+namespace Microsoft.SqlTools.ServiceLayer.LanguageExtensibility
+{
+    /// <summary>
+    /// Exception raised from machine learning services operations
+    /// </summary>
+    public class LanguageExtensibilityException : Exception
+    {
+        internal LanguageExtensibilityException() : base()
+        {
+        }
+
+        internal LanguageExtensibilityException(string m) : base(m)
+        {
+        }
+
+        internal LanguageExtensibilityException(string m, Exception innerException) : base(m, innerException)
+        {
+        }
+    }
+}