Addition of Depletion Chains for ENDF VIII.0 and JEFF3.3

[nutcasev15]

As discussed in #86 and in #2599, the OpenMC developers thought it would be good to have updated depletion chains for ENDF VIII.0 and JEFF3.3 to avoid users having to generate their own chains.

This pull request organises the depletion chains for the existing ENDF VII.1 library and includes new Python scripts for generating depletion chains from ENDF VIII.0 and JEFF3.3. The ENDF VIII.0 are based on #86. The SERPENT fission Q values were updated using ENDF VIII.0.

JEFF3.3 does not provide its NFY data in readable ENDF files, so a script to convert the NFY data to readable ENDF files is included.