app.reconstruct: allow for overwriting datasets attributes

Sometimes (often) attributes like distance, energy, etc are wrong.
In the previous system, editing a text file was enough to fix it. Now with HDF5 things are more complicated as the NX file has to be patched/recreated.

In nabu everything is in place to allow overwriting some attributes (DatasetAnalyzer wrapper, update_dataset_info_with_user_params(), etc)