added .csv files (temperature=294K) to complete the nuclides in ENDF-VII.1 library.
added creation of _elements_list.csv to avoid calling glob.glob() multiple times.
changed default database from 'ENDF_VIII' to 'ENDF_VII'.
added .hdf5 files options but not fully implemented. This is for getting doppler broadened cross-section on-the-fly with windowed multipole using openmc.data.WindowedMultipole.from_hdf5().
_elements_list.csv
to avoid callingglob.glob()
multiple times.openmc.data.WindowedMultipole.from_hdf5()
.