The wrong file was committed in @fa25403e.

This should have zero effect but you never know...

testutils.SetDefaultCompoundLib no longer needs to set the default
compound lib explicitly, as this is handled by import ost.
The method is still needed to check if a compound lib is available, and
was accordingly renamed to DefaultCompoundLibIsSet.

This sets up the compound lib upon calling import ost.
It simplifies the ost_startup.py script accordingly.
It is now possible to override the compound lib with
an environment variable: OST_COMPOUNDS_CHEMLIB

Previously, a new chain got added at the first newline after $$$$.
So if an sdf file ends with a newline, you got an unwanted empty chain.

That's the TMscore when using the other structure as reference

This is all done on the C++ level, so no intermediate files are
required. Until proper testing, this features must be considered
experimental.

Enables RNA comparison for simple chain by chain comparison.
Possible to extend to multichain functionality as implemented in
USalign.

The following issues were observed:
- warning about non-writable directory which was set as IPYTHONDIR env var
  Not very surprising, it's a directory that lives in container space...
- stale kernels
  I didn't investigate that one properly. It had something to do with bending
  around all Jupyter/IPython relevant directories to custom set directories
  in the image. Reason for doing that is potential Python modules that reside
  in user home of the host that get imported in the container. I removed the
  bending around with the full knowledge that the described problem may occur.
- version updates
  Some changes related to different Python versions between old base image
  (Ubuntu 20.04) and the new one (Ubuntu 22.04).

This makes the ligand scoring script more independent of an up-to-date
compound library, which is a strong requirement of Molck.
This was a problem for the April 2023 Modeling Championship where the
script was run with an out of date library and the element of an atom of
the ligand was silently changed, preventing the symmetry correction to
find isomorphisms and resulting in the absence of scores.

OST writes invalid atom serial numbers if they exceed the PDB format limits.
That's a feature not a bug. The new behaviour is that invalid serial numbers
don't get parsed. Any processing function working with these serial numbers
need to manually check for that. The only current effect is when reading
CONECT statements. Atoms with invalid serial numbers are not connected.