Fixes #4454: Improved asset bundle managed and used composer-asset-plugin to manage the dependencies on 3rd-party JS libraries

Fixes #4911: Changed callback signature used in `yii\base\ArrayableTrait::fields()` from `function ($field, $model) {` to `function ($model, $field) {`

Added note to config change

To get rid of confusions and errors. related to https://github.com/yiisoft/yii2/issues/4893

Fixes #4424: Added `inline` and `mimeType` options to all file downloading methods provided in `yii\web\Response`

Fixes #4489: RBAC PhpManager wasn't saving multiple assignmentsFixes #4489: RBAC PhpManager wasn't saving multiple assignments properly

fixes #4276, close #4358

Fixes #4051: Renamed `yii\caching\GroupDependency` to `TagDependency` and added support for associating multiple tags to a single cached data item

fixed indentation

fixes #4086

- Data is now stored in three separate files for items, assignments and rules. File format is simpler.
- Removed `authFile`. Added `itemsFile`, `assignmentsFile` and `rulesFile`.
- `createdAt` and `updatedAt` are now properly filled with corresponding file modification time.
- `save()` and `load()` are now protected instead of public.
- Added unit test for saving and loading data.

Fixes #4071: `mail` component renamed to `mailer`, `yii\log\EmailTarget::$mail` renamed to `yii\log\EmailTarget::$mailer`