Transform nif_ffd to per-program ffd.

* ["tes3_ffd"](https://github.com/corwinn/nifwind/commit/6711c7437bc62e9512424b93feb2b4633f1cd023)
* ["tes5_ffd"](https://github.com/corwinn/nifwind/commit/7696b3164c312a8c31399389a041b23013d0cfb2)
* ["fo3_ffd"](https://github.com/corwinn/nifwind/commit/a56bc4eb89ac13b029c2895a40be8bf3314e81be)
* ["fnv_ffd"](https://github.com/corwinn/nifwind/commit/c13fcec6b3bc286b36468e652c16cdbe5babffa3)