Incorrect character for generating docs. See http://www.yiiframework.com/doc-2.0/yii-bootstrap-activeform.html

- Removed `form_begin`, `form_end`
- Added `use()` and `ViewRenderer::uses` that are importing classes and namespaces
- Added widget dynamic functions `*_begin`, `*_end`, `*_widget`, `widget_end`
- Added more tests

Fixes #3358: Removed automatic CSRF meta tag generation by `View`. Added `Html::csrfMetaTags()` and its call to main layout files

[ci skip]

should work on HHVM too

fixes #3244

fixes #3245, #3244

The registerPlugin is not required.