CustomAtomLabels and molfile

[lpatiny]

@thsa we have the need to be able to save assignments of NMR spectra in a reliable way. During the process of assignment we may still change the molecule and therefore we can have potential atom renumbering that may be difficult to track. Also if we assign a NMR signal to an atom number we need to be certain that we don't loose this specific molfile and this is not obvious.

The diastereotopic approach that I was using till now is relatively cool because each signal has the full molecule with a tagged atom. No way to mess up. However for large molecules calculating those diaIDs is too slow and editing the molecule is problematic.

I was wondering if we could add customLabels to each atoms and that those customLabels could be saved / loaded from the molfile.

In molfile specification I see 2 fields that could contain the labels: