Can either be pushed to standalone internal file format
or serve as starting point for MMTF / binaryCIF implementation
in OST. The stored data is kind of similar...

same as commit 69f90c46

makes it easier to re-use elsewhere

The test_Interpolate unit test has been reported to fail when executed
on different platforms (arm64 in this case).

The test_simulation_energy_calculations unit test compares the potential
energy of crambin after 200 steps steepest descent with a reference value.
Depending on OpenMM version / hardware, we might get slight differences
that propagate through the minimization.

CMake now takes care of extracting the major, minor and patch version of Python

I assume there was good reason to add it...

You might have to adapt CMake flags when building OpenStructure to variables specified here:
https://cmake.org/cmake/help/latest/module/FindPython.html

First entry is about adding the -pthread flag to resolve linking
problems. Has been observed on the scicore cluster and reported
by Yuri (FreeBSD 12.2).

The previously used URLS were redirected to the new ones but redirection
is not guaranteed to last indefinitely.
related documentation: https://www.rcsb.org/pages/download/http

Unit tests successfully run through with Python 3.9 on Fedora 33 (no GUI)

This caused trouble when switching OpenGL context for offscreen
rendering (DNG image export)