field dependent empty_data option description

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | #4007

- [ ] checkbox
- [x] choice
- [x] collection
- [ ] country
- [ ] currency
- [x] email
- [ ] entity
- [x] file
- [ ] form
- [x] integer
- [ ] language
- [ ] locale
- [x] money
- [x] number
- [x] password
- [x] percent
- [ ] radio
- [x] search
- [x] text
- [x] textarea
- [ ] timezone
- [x] url

This is not yet complete. But I'm not sure if I like the way it looks now with the default value below the ``note`` directive.