many updates:

MINT structure is now allocated as a substructure of the star, which means we can no longer memcpy stardatas and stars when using MINT. The functions copy_star and copy_stardata do this for us, of course, and have been updated appropriately.

fixed up the old nuclear network code, this is work in progress but makes things much more transparent and flexible

fixed the nuclear networks to use enums not macros, and these can be set on the command line

fixed bug in MINT that caused problems when 1-X-Y!=Z. this is a fudge that may fail later!

fixed the nuclear isotopes list so we have light and heavy isotopes, and fixed the many functions that use the heavy elements so they compile (and do nothing) with the heavy elements off.