fix bugs of BlameableBehavior in console application. In console application, \yii\console\Application doesn't have `getUser()` method. Use BlameableBehavior in console application will cause an exception.

fix a typo.

Rewritten testing introduction, added environment setup to README.md, removed empty pages that were not referenced

Upgrade jquery.inputmask to Version: 3.1.1

Added yii\web\Request::setRawBody()

link fix

Enh #4062 : Added 'caseless' option to `yii\helpers\BaseFileHelper::findFiles()`

Enh #4424: Added `forceDownload` parameter to `yii\web\Response::xSendFile()`

Enh #3459 : Added logging of errors, which may occur at `yii\caching\FileCache::gc()`

`yii\base\ErrorHandler::handleError()` adjusted keeping native error processing on error reporting miss match.