Incorrect zero values in FactorHierarchy.json

[xhorsky1]

There are invalid zero values ("0E+3", "0E+3", etc.) present in the output file FactorHierarchy.json. An example of such file is attached.

20240602_FactorHierarchy.json

[hojkas]

This line was at fault https://github.com/sb-ncbr/pdb-data-cruncher/blob/master/src/data_transformation/factor_hierarchy_updater.py#L124

In branch normalize-zero-numbers-on-output, there is a commit with draft proposed change to fix this.

Please review and test before using, it is merely a draft and only partially tested.