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/AzureUserAccount.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 System.Collections.Generic;
@@ -53,7 +54,7 @@ namespace Microsoft.SqlTools.ResourceProvider.DefaultImpl
                    CommonUtil.SameString(other.TenantId, TenantId);
             // TODO probably should check the AllTenants field
         }
-        
+
         /// <summary>
         /// Unique Id
         /// </summary>
@@ -68,7 +69,7 @@ namespace Microsoft.SqlTools.ResourceProvider.DefaultImpl
                 this.uniqueId = value;
             }
         }
-        
+
         /// <summary>
         /// Returns true if user needs reauthentication
         /// </summary>
@@ -77,7 +78,7 @@ namespace Microsoft.SqlTools.ResourceProvider.DefaultImpl
             get;
             set;
         }
-        
+
         /// <summary>
         /// User display info
         /// </summary>