AUI-1585

Ticket: [AUI-1585](https://issues.liferay.com/browse/AUI-1585)

I simplified the logic (most of those conditionals weren't being executed) to this: If the field is `checkable`, place the `.form-validator-stack` at the end of the `.form-group`, otherwise just place it after the field in question.

I saw the error you mentioned involving radios and checkboxes in the demo. It looks like the cause is that the `.checkbox` is not wrapped in a `.form-group`. If this is correct/possible markup, I can take another look.

Thanks!