Fixes #4823 and #6005: `yii message` accuracy and error handling were improved by using PHP tokenizer instead of regular expressions. Removed eval() as well.

Fixes #6107 and #6112: `yii message` was emptying existing translations and incorrectly writing not yet translated strings in .po in case of multiple categories

Fixes #5954: `yii message` command now shows user friendly error if it's not able to parse source file

Fixed order of checking config `format` property

Improved checks where substr_compare is used, replaced more substr + comapre cases with substr_compare

Fixes #4453: `yii message/extract` wasn't properly writing to po files in case of multiple categories

Obsolete keys searching isn't work when we have serveral categories for tranlation with DbMessageSource. Obsolete array filled with last message category only, because it'll always overwritten.

Added `yii\console\Controller::EXIT_CODE_NORMAL` and `yii\console\Controller::EXIT_CODE_ERROR` constants, `yii\console\MigrateController` now returns `yii\console\Controller::EXIT_CODE_ERROR` in case of failed migration

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

issue #3026

issue #2852

fix code style