Single Horse with only Description as Official ID

[mkm1879]

These get translated to a LargeAnimalGroup with quantity 1 in my translation from the eCVI. This is because our definition of LargeAnimal has Tag and TagNumber required. Not all individual large animals actually require a "tag number."

Proposed solutions:

1. Allow description as alternative to tag number in Large Animal.
2. Make sure LargeAnimalGroup includes the concept of a single animal without official ID tag (or chip).
3. Put horse description as AnimalTag/Number even when listed as "other ID" in source.