Introduce Freemartin to icarAnimalGenderType

[Busfi3ld]

Would like to add Freemartin to icarAnimalGenderType. Freemartin is a commonly used term in the UK for an incomplete Femail animal, usually born as a twin. We could use FemaleNeuter as the animal is in the same or similar state, however does not feel accurate for a couple of reasons:

1. Implies that the animal was Femail and has been operated on to become FemaleNeuter
2. Is not a recognised term with dairy sector.

[cookeac]

Makes sense - let's just ensure that the gender types work across all livestock species and production systems, not just dairy cows.

[cookeac]

Reviewed 2025-02-20.
Noted that Freemartinism is multi-species - https://www.researchgate.net/publication/256293263_Freemartinism_in_Cattle
Agreed to add this.

We would benefit from some documentation of these values.