Add static page

Correction of many warnings code inspection.

Adjustments code according to the standards.
Adding missing PHPDoc comment.

Fixes #3121: `yii\base\Application::bootstrap` may fail to load some components if they are specified as class names

Fixes #3042: `yii\widgets\Pjax` should end application right after it finishes responding to a pjax request

Add yii\bootstrap\ActiveForm to the bootstrap guide

http://www.yiiframework.com/forum/index.php/topic/53430-appasset-questions-getting-404-error-on-asset-files/page__gopid__246055#entry246055

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

Update ActiveQuery.php

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()`

Implement new RBAC PhpManager

Update ActiveRelationTrait.php

Update gii guide.

Hide debug toolbar when media = print

Update model.md

Add `whenClient` description

fix https://github.com/yiisoft/yii2/issues/3050

fixes for https://github.com/yiisoft/yii2/issues/951#issuecomment-25934549