Harmonize transition notations between NIST and ADAS

[dvezinet]

I've updated vcsp code in github to include functions to fetch nist data and synchronize transition notations with ADAS PEC. If you just want to pull functions to read nist and adas pec data (especially transitions written in Eissner notation - Ar and W cases), you can take a look __spectra__.py lines from 445 to 713 (https://github.com/cfs-energy-internal/vcspectra/blob/main/spectra.py).