kitemmodels python bindings

[Harald Sitter]

Ahoy ahoy,

I gave packaging the new python bindings in kitemmodels a stab and was
hoping for some peer review as I haven't created a python package in
years.

https://packaging.neon.kde.org/frameworks/kitemmodels.git/commit/?id=8f6ffd64e7f7655f4780697a8046b09bcd2432e5

One thing I am particularly unsure about is whether or not
usr/lib/python3.Y/ is an acceptable installation path or if indeed
coercing it to be usr/lib/python3/ is the way to go.

HS