Python 3.x support

[neomonkeus]

Update niflib to use Python3.x

[BlazesRus]

After having pip install modernize, try:
py -3.9 -m modernize -w FILENAME
py -3.9 -m pyupgrade --py3-plus --py36-plus --py37-plus --py38-plus FILENAME
with filename replaced with target files(and 3.9 replaced with current python version)(worked for upgrading docsys to 3.x)
Manually replace the .imports such as
from .nifxml import Member, Compound, Block
into
from nifxml import Member, Compound, Block
And possibly also delete the init.py files so python 3.x can autopackage without needing from future imports

[neomonkeus]

Feel free to PR back in to the repos, I see that you have alot of working going on.
If you can drop by - https://discord.gg/y6pHsh9Dha

[BlazesRus]

Discord link invalid(all that stuff I'm working on is just hobbyist stuff and most of it are planned components of other code)
P.S. Also trying to set up a C++ replacement of DocSys that supports 0.9.2 nifxml (including more than one expression test formulas) :)

[neomonkeus]

Sorry might have expired, updated there.
The last piece of work that jon did was to add some support within the nif.xml library itself to generate docs, with the intent that it should be self describing and not have to rely on external tooling.
I have a PR open for a minor bug, but haven't had time to look much further past it I am afraid.
All contributions are welcome as most project could do with much love to get them up to using latest versions.