type validation adjusted

This one is related with this [issue](https://github.com/yiisoft/yii2/issues/3774) .
to be true we can argue here forever ) dont have any arguments except those said above. But `FileValidator` code that was before, was really hard to understand and maintain. I event spend some time during debug because something was wrong with switch case when i put all `validateType` logic inside `elseif` `type` section. Overall you are core developer.