Orphan uniqueness

https://osraav.atlassian.net/browse/OSRA-264

- orphan records validated for uniqueness by orphan's name, father's name & mother's name
- importer refactored to perform an additional validation on each new Orphan record

_Shoulda matchers were having issues with the uniqueness validation due to association requirements on new orphan objects. Rather than continuing to fight with them, I wrote a test by hand and only included one basic scenario as this validation is standard Rails. Let me know if you think that's inadequate._
prefer
```
orphan = create :orphan
duplicate_orphan = orphan.dup
```