Fixes #5627: Added `yii cache/flush-schema` console command to flush DB schema cache of a given database connection

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

Fixed `yii\console\controllers\AssetController` breaks CSS URLs in case target file localed at `yii\web\AssetManager::basePath` root

Fixed `yii\console\controllers\CacheController` does not check if cache component instance of 'yii\caching\Cache'

close #5055

related to #4792, close #4874

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

`yii\console\controllers\AssetController::actionTemplate()` advanced to include `jsCompressor` and `cssCompressor` to the template.