Custom User Data

@esoergel @twymer
so i was thinking something like this (i don't really know if this would work and it's definitely not a huge thing if it doesn't):

```python
class CustomFieldsEditView(View):
    urlname = "fields_edit_view"
    
    @property
    def page_name(self):
        return self.spec.page_name

    def dispatch(self, request, domain, field_type, *args, **kwargs):
        self.domain = domain
        # this is some magic function that gets whatever config you need
        # should 404 if the field_type isn't a known thing
        self.spec = get_spec_from_field_type(field_type)  
        return super(CustomFieldsEditView, self).dispatch(domain, *args, **kwargs)
```

and then in your urlconf you'd have something like:

```python
url(r'^custom_fields/(?P<field_type>[\w\-:]+)/$', CustomFieldsEditView.as_view(), name=CustomFieldsEditView.urlname),
```

It might be worth doing a second use case now to validate that the steps for rolling this out to groups/products/locaitons/etc. makes sense and doesn't involve too much repeated scaffolding (which is essentially what I'm trying to avoid)