refs #140, Adapt the validation view in order to skip filefield
refs #140, Adapt the validation view in order to skip filefield

This commit comes with multiple changes inside the validation view.
First, the method are copied from django POST view in order to get
more flexibility at the integration time. The view can be easily
overrided with common method, like `get_form_class` `get_form_kwargs`,
etc. Second, the field_map parameters newly inserted in the formfield
fatory is used in order to add a FileFieldBuilder which raise "
SkipField" at the built time.

novafloss/django-formidable