Add function to pull nuclear data from OpenMC nuclear data, GNDS, or ACE files

[MicahGale]

I was going through the documentation for MC/DC materials, and it wasn't clear to me how to create a nuclide with a continuous energy nuclear data set. Obviously users wouldn't manually specify this. Rather they would pull it from a file. It would be nice to be able to pull this from an OpenMC HDF5 file, or if really necessary, an ACE file.

[clemekay]

This is something we've discussed and plan to implement, thanks Micah!