return value would not be a valid array when json encoded after unlink().

fixes #6065

close #6061

- docs/guide-ja/structure-extensions.md - prepared for translation [ci skip]
- docs/guide-ja/structure-assets.md - small changes [ci skip]
- docs/guide-ja/structure-extensions.md - WIP [ci skip]
- docs/guide-ja/structure-extensions.md - completed [ci skip]
- docs/guide-ja/structure-widgets.md - broken link fixed [ci skip]

close #6062

Fixes #6049: `yii\db\Connection::getSchema()` for Oracle should return false when the table does not exist. Oracle does not support `ON UPDATE` clause.

Fix batchInsert bug in oci. default batchInsert sql is ``` insert into tableName(col1, col2, col3...) value(`col11`, `col12`,`col13`.... ),(`col21`, `col22`,`col23`.... ); ``` which is illegal in oracle db. Change it to ``` insert into tableName(col1, col2, col3...) select 'col11', 'col12', 'col13' from dual union select 'col21', 'col22', 'col23' from dual union select 'col31', 'col32', 'col33' from dual; ```

oracle db doesn't support `ON UPDATE` in FOREIGN KEY. remove `ON UPDATE` section in method `addForeignKey`.

fix oci bugs: \yii\db\oci\Schema::findColumns($table) return true when table doesn't exist When table doesn't exist, query in method `findColumns` return empty array instead of throw a exception.

thanks to @pana1990

close #6060

Broken link

[asset bundles](structure-asset-bundles.md)
change on
[asset bundles](structure-assets.md),

Update rest-error-handling.md

Should be parentheses instead of square brackets

Use case:

```
    echo GridView::widget([
        ...
        'columns' => [
            ...
            [
                'attribute' => 'created_at',
                'label' => '<span data-toggle="tooltip" class="glyphicon glyphicon-time" title="'.Yii::t('app', 'Created At').'"></span>',
                'encodeLabel' => false,
                ...
            ],
```

fixes #4745

groovy is now always on in ES 1.3.0

fixes #5662

Some Annotation Typos

close #6029

close #6036

- prepared for translation [ci skip]
- docs/guide-ja/structure-widgets.md - changed "コンテント" to "コンテンツ" [ci skip]
- docs/guide-ja/* - changed "ドキュメンテーション" to "ドキュメント" [ci skip]
- docs/guide-ja/intro-yii.md - inserted the Chinese character "易" [ci skip]
- docs/guide-ja/structure-assets.md - WIP [ci skip]
- docs/guide-ja/structure-assets.md - completed [ci skip]

close #6037

Fixes #5799: `yii\bootstrap\ButtonGroup::buttons` can take all options that are supported by `yii\bootstrap\Button`

Pass all the button's config array to Button::widget() instead of creating new one item by item. Now allowed to pass in ButtonGroup button's configs any possible attributes(like tagName, encodeLabel, etc).

Rest versioning spanish guide changes and fixes [skip ci]

[skip ci] Spanish guide

More Spanish guide changes and fixes

Typo fix in guide-ru

Fixes #6018: When setting the `encode` option via `yii\widgets\ActiveRecord::errorOptions`, it works the other way around [skip ci]