Merge `nuclear` with Carsus

[andrewfullard]

Is your feature request related to a problem? Please describe.
It's difficult to install nuclear, carsus and tardis at the same time due to environment conflicts, plus adding another package is always annoying.

Describe the solution you'd like
Merge the code of nuclear into Carsus, while at the same time improving the parsing capabilities of nuclear.

• Issues reading isotopes with metastable states e.g. Mn52
• Issues reading some isotopes with odd data e.g. V48

[epassaro]

I thought nuclear used the same environment file as tardis, has this changed recently?

[andrewfullard]

It changed when we moved away from pyne

[andrewfullard]

Superseded by #325