close #5355

Fixes #5232 and #5231

as discussed before, better do this change before RC to avoid breaking BC in GA.

Fixes #5143: yii\bootstrap\ActiveField::label() should not encode label if it is explicitly specified. [skip ci]

- in composer the `~` operator is just a shortcut for `~1.0` = `>=1.0.0,<2.0.0`
  it does not prevent dev versions to be installed but neither does `1.*`
- dev versions are constrolled via `minimum-stability` setting and the
  `@dev`, `@beta`, `@stable`,... settings.
- setting bower packages that ship compiled files only with the stable
  release to use `@stable` in composer.json of the applictaions. This
  setting can be removed when we remove the `minimum-stability=dev`
  setting after GA.

Fixes #5058: `yii\helpers\Html::activeCheckbox()` and `activeRadio()` will generate labels by default using the corresponding attribute labels

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

Better fix for #3443 that does not break BC and allows widget to be extensible.