Update ActiveForm.php

Incorrect character for generating docs. See http://www.yiiframework.com/doc-2.0/yii-bootstrap-activeform.html
Merge pull request #3991 from ychongsaytc/patch-2

Update ActiveForm.php
added more unit tests to widgets\Breadcrumbs and 100% coverage.
Merge pull request #3995 from njasm/master

Added more unit tests to widgets\Breadcrumbs and increased coverage to 100%
Fixes #3996: Traversing `Yii::$app->session` may cause a PHP error
Create caching-overview.md

Add translate for caching-overview.md
Merge pull request #3998 from dementorpasha/patch-2

Create caching-overview.md
Fixed Inflector::slug to work properly with numbers
Finished filter section [skip ci]
Translation's normalization and correction
Merge remote-tracking branch 'upstream/master'
Update from remote