Iterate over the form using form.__iter__ to retrieve a more complete field

Hi there!

Not sure if this is necessary but I found that `field.label` in the existing instance would always be empty, unless specified. I noticed that if you iterate over the fields in the form using the forms `__iter__` method you are returned a BoundField, which does some niceties like set the label to a `pretty_name`

There may be some more things that can be done given this field is now passed around, perhaps improving the widget rendering :)