Control grous can contain multiple inputs in the case of mappings and sequences.
We only want to mark red those `input` (and `radio`, `select` etc) tags that are "directly" included in a `.error` element.
See https://github.com/Pylons/deform/issues/167
Merge pull request #58 from silviot/master

Fix all fields being marked invalid if another field in the same mapping/sequence is