fixes #4105, close #4376

`yii\web\Request::cookieValidationKey` is now automatically generated by the installation script for the basic and advanced application templates

fixes #4276, close #4358

Example

```
['profit', 'number', 'min' => 0.01],
```

Value 0.01 is allowed

Fixes #3443: Fixed `yii\bootstrap\Nav` and `yii\bootstrap\Dropdown` were generating wrong ids for submenus

fixes #4343

Fixes #4318: `yii\helpers\Html::ul()` and `ol()` will return an empty list tag if an empty item array is given

This is based on the code from Yii 1.1.14 by Ivo Kund.

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

Added `beforeCopy`, `afterCopy`, `forceCopy` properties to AssetManager

fixes #4209