yii\captcha\CaptchaValidator->createCaptchaAction() error

Fixes #2003: Added `filter` property to `ExistValidator` and `UniqueValidator` to support adding additional filtering conditions

fixes #1993

fixes #1984

All the quotation marks must be screened by adding a backslash before them. Otherwise we cannot generate .mo file.

A bit less stricter check as suggested by @qiang: https://github.com/yiisoft/yii2/commit/2aa8fc71714134feac3f0a09dd61837d920be534

Files are generated using message/extract command.
E.g.: ./yii message/extract message/config.php po

init of advanced application now allows to specify answer for overwriting files  via init --overwrite=n