Fix #549 -- Multiple PDF ticket layouts (#938)

- [x] Data model
- [x] CRUD
- [x] Editor
- [x] Migration from old settings
- [x] Clone files when copying events
  - [x] badges?
- [x] Actual ticket output
- [x] Default layout on event creation
- [x] Link well from ticketing settings
- [x] Tests
- [x] Shipping plugin
  - [x] Migration
  - [x] Settings
  - [x] Create default
- [x] API

src/pretix/plugins/badges/forms.py

@@ -19,6 +19,7 @@ class BadgeItemForm(forms.ModelForm):
         event = kwargs.pop('event')
         super().__init__(*args, **kwargs)
         self.fields['layout'].label = _('Badge layout')
+        self.fields['layout'].empty_label = _('(Event default)')
         self.fields['layout'].queryset = event.badge_layouts.all()
         self.fields['layout'].required = False