`VarDumper::export()` applied over framework.

Handle invalid code sequences in Html::encode()

Fix for #3232 var export

[ci skip] Korean Language translation

Update output-data-providers.md

Update UniqueValidator.php

Modified a bit, better?

defaultOrder this is often used for everyone

Rename errorHandler to getErrorHandler()

Tests excess dump removed

fixes #3353

issue #3494

add "ko" value for languages array