Added encodeLabel param to \yii\grid\DataColumn

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 #5367: Added `yii\grid\DataColumn::encodeLabel`
Update rest-error-handling.md

Should be parentheses instead of square brackets
Merge pull request #6051 from anders-akero/patch-1

Update rest-error-handling.md
Broken link

[asset bundles](structure-asset-bundles.md)
change on
[asset bundles](structure-assets.md),
Merge pull request #6052 from ArgosOleg/patch-1

Broken link
fixed phpdoc

thanks to @pana1990

close #6060
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.
oracle db doesn't support `ON UPDATE` in FOREIGN KEY. remove `ON UPDATE` section in method `addForeignKey`.
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; ```
Fixes #6049: `yii\db\Connection::getSchema()` for Oracle should return false when the table does not exist. Oracle does not support `ON UPDATE` clause.
guide ja

- 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
docs/guide/structure-extensions.md - typo fixed [ci skip]

close #6061
fixed unlink() for array valued attributes

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

fixes #6065
Update runtime-bootstrapping.md

close #6066
docs/guide-ja/runtime - added 2 sections [ci skip]

- docs/guide-ja/runtime-overview.md - added [ci skip]
- docs/guide-ja/runtime-bootstrapping.md - added [ci skip]
- docs/guide-ja/runtime-bootstrapping.md - added links to OPCache and APC [ci skip]

close #6067
Update tutorial-advanced-app.md

Fix backend url

close #6070