fixes issue #3989

Fixes #4080, FileHelper::removeDirectory() symlinks handling enhancements

Russian translation of concept-behaviors.md

[ci skip]

1. Added proper handling and support of the symlinked directories.
2. Added $options parameter.

Translate docs to Chinese.

Fixes #1452: Added `Module::getInstance()` to allow accessing the module instance from anywhere within the module

split typecast method into two

structure-overview translation to spanish

add autocomplete for model class field

small mistakes in service locator guide.

besides, what is `app\components\SolrService`?

Oracle Schema fix

Fixes #4071: `mail` component renamed to `mailer`, `yii\log\EmailTarget::$mail` renamed to `yii\log\EmailTarget::$mailer`

Revert "Gii `*Search` model generator fix"

Fixes #3101: Improved handling of log target failures