Grid view ActionColumn buttons names like `{controller/action}`

For example:

```php
<?= GridView::widget([
	'dataProvider' => $dataProvider,
	'filterModel' => $searchModel,
	'columns' => [
		[
			'class' => 'yii\grid\ActionColumn',
			'template' => '{answer/index}',
			'buttons' => [
				'answer/index' => function ($url, $model) {
					return Html::a('<span class="glyphicon glyphicon-folder-open"></span>', $url, [
						'title' => Yii::t('yii', 'Go to answers grid'),
					]);
				},
			],
		],
		'id',
		'title',
		'body:ntext',
		'create_time:datetime',
		'update_time:datetime',
		['class' => 'yii\grid\ActionColumn'],
	],
]) ?>
```