Offline tool for converting HDF5 to .dat

Issue tracked here: https://jira.esrf.fr/browse/DPDEV-287

Could all .dat files (from sample changer and hplc runs) which are directly accessible on ISPyB for our users to be send to ICAT data portal. Majority of our users use .dat files to further data processing and extraction of them from data portal is not convenient.

@jerome said that the script is available here, and is part of the freesas software: https://github.com/silx-kit/freesas/blob/main/src/freesas/app/extract_ascii.py