Support "SQL" settings in addition to MSSQL (#398)

* Support "SQL" settings in addition to MSSQL
- Handles having 2 separate configuration definitions and merging / treating them as 1 throughout the app
- If a settings group such as Intellisense is defined on mssql, it will override any generic SQL properties
- Retains backwards compatibility with existing settings.

src/Microsoft.SqlTools.ServiceLayer/SqlContext/SqlToolsSettingsValues.cs

@@ -0,0 +1,55 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.SqlTools.Utility;
+using Newtonsoft.Json;
+
+namespace Microsoft.SqlTools.ServiceLayer.SqlContext
+{
+    /// <summary>
+    /// Class that is used to serialize and deserialize SQL Tools settings
+    /// </summary>
+    public class SqlToolsSettingsValues : ISqlToolsSettingsValues
+    {
+        /// <summary>
+        /// Initializes the Sql Tools settings values
+        /// </summary>
+        public SqlToolsSettingsValues(bool createDefaults = true)
+        {
+            if (createDefaults)
+            {
+                IntelliSense = new IntelliSenseSettings();
+                QueryExecutionSettings = new QueryExecutionSettings();
+                Format = new FormatterSettings();
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the detailed IntelliSense settings
+        /// </summary>
+        public IntelliSenseSettings IntelliSense { get; set; }
+
+        /// <summary>
+        /// Gets or sets the query execution settings
+        /// </summary>
+        [JsonProperty("query")]
+        public QueryExecutionSettings QueryExecutionSettings { get; set; }
+
+        /// <summary>
+        /// Gets or sets the formatter settings
+        /// </summary>
+        [JsonProperty("format")]
+        public FormatterSettings Format { get; set; }
+
+        /// <summary>
+        /// Gets or sets the formatter settings
+        /// </summary>
+        [JsonProperty("objectExplorer")]
+        public ObjectExplorerSettings ObjectExplorer { get; set; }
+    }
+}