Add configuration change notification event handler.

Clean up code a bit more to remove unneeded code.
Better integrate the diagnostic callback code.

ServiceHost/LanguageSupport/LanguageService.cs

@@ -0,0 +1,57 @@
+//
+// 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.EditorServices;
+using Microsoft.SqlTools.EditorServices.Session;
+
+namespace Microsoft.SqlTools.LanguageSupport
+{
+    /// <summary>
+    /// Main class for Language Service functionality
+    /// </summary>
+    public class LanguageService
+    {
+        /// <summary>
+        /// Gets or sets the current SQL Tools context
+        /// </summary>
+        /// <returns></returns>
+        private SqlToolsContext Context { get; set; }
+
+        /// <summary>
+        /// Constructor for the Language Service class
+        /// </summary>
+        /// <param name="context"></param>
+        public LanguageService(SqlToolsContext context)
+        {
+            this.Context = context;
+        }
+
+        /// <summary>
+        /// Gets a list of semantic diagnostic marks for the provided script file
+        /// </summary>
+        /// <param name="scriptFile"></param>
+        public ScriptFileMarker[] GetSemanticMarkers(ScriptFile scriptFile)
+        {
+            // the commented out snippet is an example of how to create a error marker
+            // semanticMarkers = new ScriptFileMarker[1];
+            // semanticMarkers[0] = new ScriptFileMarker()
+            // {
+            //     Message = "Error message",
+            //     Level = ScriptFileMarkerLevel.Error,
+            //     ScriptRegion = new ScriptRegion()
+            //     {
+            //         File = scriptFile.FilePath,
+            //         StartLineNumber = 2,
+            //         StartColumnNumber = 2,  
+            //         StartOffset = 0,
+            //         EndLineNumber = 4,
+            //         EndColumnNumber = 10,
+            //         EndOffset = 0
+            //     }
+            // };
+            return new ScriptFileMarker[0];
+        }
+    }
+}