Give possibility to pass arg to schema validator

[amoriarty]

Hello everyone.

I add the possibility to pass arg to the schema validator, the same way it is done for the custom validator.

Once again, I'm not sure it was the way to do it, but at least it is there.

[Keats]

I will need to look a this codebase again before doing a proper review, to be honest I don't remember much about it.