Automatic generation of <div id="{controller}-{action}"> ... </div> for each views

Delete:
```
<div class="site-about"> ... </div>
<div class="site-contact"> ... </div>
<div class="site-error"> ... </div>
<div class="site-index"> ... </div>
<div class="site-login"> ... </div>
```
from templates and add ```<div id="<?= Yii::$app->controller->id . '-' . Yii::$app->controller->action->id ?>"> ... </div>``` to layouts/main.php