Fixes #3066: `yii\db\mssql\Schema::getTableSchema()` should return null when the table does not exist.

PHPDoc comment does not match function or method signature
Update PHPDoc Comment

Adjust code standard

Replaced `clearAll()` and `clearAllAssignments()` in `yii\rbac\ManagerInterface` with `removeAll()`, `removeAllRoles()`, `removeAllPermissions()`, `removeAllRules()` and `removeAllAssignments()`

Fixes #3091: Fixed inconsistent treatment of `Widget::run()` when a widget is used as a container and as a self-contained object

Re-implemented RBAC by following more closely to the original NIST RBAC model. Dropped `yii\rbac\PhpManager`.

issue #3026

fixes #3034