l0rdn1kk0n/wicket-bootstrap — pull request #416 by romueller (2014-07-16 19:14:17+00:00)
Title: FormGroup should not implement IFormModelUpdateListener

- this interface should only be implemented by form components
to update their _own_ model
- the wicket Form already visits all its child form components
and call their updateModel method
-> the updateModel method of the FormGroup causes that the
updateModel method of each of its children gets called twice