title: Yii2 advance replace url backend/web to admin
body: <p>In the yii2 advanced application, need to show admin instead of backend/web and default route to this admin url.</p>
  <p><code>http://localhost/yapp/backend/web/site/index</code> to <code>http://localhost/yapp/admin/site/index</code> and when running application it should redirect to <code>http://localhost/yapp/admin</code></p>