Add linting for copyright and unused usings (#1416)

* Add linting for copyright and unused usings

* Add one more + comment

* Enforce in build and fix errors

* Fix build

src/Microsoft.SqlTools.ResourceProvider.DefaultImpl/SqlAzureResource.cs

@@ -1,6 +1,7 @@
 //
 // 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 Microsoft.SqlTools.ResourceProvider.Core;
@@ -17,7 +18,7 @@ namespace Microsoft.SqlTools.ResourceProvider.DefaultImpl
         private readonly Models.Server _azureSqlServerResource;
 
         /// <summary>
-        /// Initializes the resource 
+        /// Initializes the resource
         /// </summary>
         public SqlAzureResource(Models.Server azureResource) : base(azureResource)
         {