generic way to support scriptable operations (#438)

* implemented a generic way to support scriptable operations

src/Microsoft.SqlTools.ServiceLayer/Utility/IScriptableRequestParams.cs

@@ -0,0 +1,18 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+
+using Microsoft.SqlTools.ServiceLayer.TaskServices;
+
+namespace Microsoft.SqlTools.ServiceLayer.Utility
+{
+    public interface IScriptableRequestParams : IRequestParams
+    {
+        /// <summary>
+        /// The executation mode for the operation. default is execution
+        /// </summary>
+        TaskExecutionMode TaskExecutionMode { get; set; }
+    }
+}