Set ZA according to LANL rules?

[whaeck]

[Future work - documentation]
It doesn't need to be here, but it may be worth documenting the historical convention on handling metastables, namely:

1. The constructor arguments for Z and A are unmodified by S. Tc99m should not have A = 499.
2. The ZAID should be ZZZ[AAA + 300 (S > 0) + 100 S].NNx.
3. Am242m1 and Am242 are swapped (LANL convention - NNDC doesn't swap).

You can rightfully argue that the responsibility is on my team's side to document this. I intend to do so very soon. I just thought it would be easy for someone to have no idea about this weirdness if they're only working on this side.

Originally posted by @cjosey in #48 (comment)