Add new guide upload-file

Fix Gii template variables order

Improved `yii\helpers\Inflector::slug` to support more cases for Russian, Hebrew and special characters

Fixes #3687: Default `sourceLanguage` and `language` are now `en-US` in order for i18n formatter to work correctly

RU translations of few guide articles

Translated and orpho fixed.

Translated

Additional `Application` property for `$formatter`

fix typo

Остался последний раздел

Fix case for ActiveField::checkboxTemplate use

Fixes #3716: `DynamicModel::validateData()` does not call `validate()` if the `$rules` parameter is empty

Fix label() method and make more templates configurable

fix #3478

Fixes #3715: Fixed the bug that using a custom pager/sorter with `GridView` may generate two different pagers/sorters if the layout configures two pagers/sorters