Refactor packaging, part I

Relates to #75 (closed).

Move all project info to pyproject.toml.

Tasks:

• Static Project Info
• Register and run versioneer
• Register Cython extension modules
• Clean up package data files & manifest
• Remove quicktest action from setup.py and realize quicktests some other way -> introduced quicktest.py

Notes:

• The quicktest command in setup.py uses the distutils command interface, but distutils is deprecated since Python 3.10. We must find some other way to realize quicktests.

.gitlab-ci.yml

@@ -109,7 +109,7 @@ ubuntu:
   before_script:
     - apt-get -y remove python3-sympy
     - ln -s /usr/include/locale.h /usr/include/xlocale.h
-    - pip3 install `grep -Eo 'sympy[>=]+[0-9\.]+' setup.py | sed 's/>/=/g'`
+    - pip3 install `grep -Eo 'sympy[>=]+[0-9\.]+' pyproject.toml | sed 's/>/=/g'`
     # - pip3 install `grep -Eo 'sympy[>=]+[0-9\.]+' setup.py | sed 's/>/=/g'`
   script:
     - export NUM_CORES=$(nproc --all)