- add a tip that rbac.php is needed to create manually when using PhpManager.
- update that RbacController example needs to import Yii namespace.

- 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

Change git clone git@github.com:yiisoft/yii2-app-basic.git to 
git clone https://github.com/yiisoft/yii2-app-basic

Fixed typo in validation guide

We need an image of the CRUD preview (or we need to change the text).

Not clear how define('YII_ENV', 'dev') creates the YII_ENV_DEV
constant. Seems like an odd bit of magic that may confuse others…

Should it be “quality of these articles may not be as good”?