Add decay information to materials

Leverage ENSDF database information to add decay data to materials. Only photons are currently supported. This also fixes some bugs in the current ENSDF parser.
Mostly just the weird colloquialisms that exist in the detection community. Even though it was originally "alpha-rays", "beta-rays", "X-rays", and "gamma-rays", now its commonly "alphas", "betas", "X-rays", and "gamma-rays". `gammas()` is acceptable.