ECDC-3109: Allow dynamic path

Created by: kmurica

Issue

Closes https://jira.esss.lu.se/browse/ECDC-3109

Description of work

Making changes to how the HDF5 file path is handled both internally and as input in the config .ini file to the file writer. By requirements, if the hdf-output-prefix is not provided in the .ini file, the default should be the root directory (the rest of the path might come from NICOS for example).

Reminder

Changes should be documented in changes.md