Simplified ArrayTrait::fields() default implementation since it works fine w/ just field names as values

[ci skip] pt-BR start-hello

Fixes #2380: `yii\widgets\ActiveForm` will register validation js even if there are not fields inside

Fixes #3240: Added support for assigning an anonymous function to `yii\widgets\ActiveForm::fieldConfig`

fixes #4931

issue #4719

New syntax:

```
[link to guide](guide:file-name.md)
[link to guide](guide:file-name.md#subsection)
```

fixes #4719

Fix typos and semantic errors in Serbian translation

When an ID is found to be in both `Application::controllerMap` and `Application::modules`, the former will take precedence

Fixes #4920: `yii\filters\auth\CompositeAuth` should not trigger error as long as one of the methods succeeds
Fixes #3177: `yii\filters\auth\CompositeAuth` will send out challenges from all auth methods

Update UrlManager

Console help refactoring

Added information about --appconfig to output of help command, color option is now passed to controller whose help we're getting

Fix typo in security-authorization.md