add table designer handlers (#1269)

* add table designer handlers

* add comments

src/Microsoft.SqlTools.ServiceLayer/TableDesigner/Contracts/Components/ComponentPropertiesBase.cs

@@ -0,0 +1,28 @@
+//
+// 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.TableDesigner.Contracts
+{
+    /// <summary>
+    /// Base class for component properties
+    /// </summary>
+    public abstract class ComponentPropertiesBase
+    {
+        public ComponentPropertiesBase()
+        {
+            this.Enabled = true;
+        }
+
+        public string Title { get; set; }
+
+        public string AriaLabel { get; set; }
+
+        public Nullable<int> Width { get; set; }
+
+        public bool Enabled { get; set; }
+    }
+}