Implement an end-to-end solution for interrupted sessions and duplicated fieldmaps

Currently, we have only a short description of dealing with duplicated fieldmaps in the case of interrupted sessions. We should have an end-to-end solution, especially that this situation is expected to happen. I propose to implement the following steps:

• Delete the obsolete fMRI scans, if they have been exported from the scanner.
• Add _run-<index> to multiple fieldmaps automatically with BIDScoin map file. Use {run: <<1>>} construct. This will, however, add run-1 to the names of the not duplicated fieldmaps too.
• Implement a tool in bids-util scripts to overwrite the automatically assigned IntendedFor values (which would be correct in case of uninterrupted acquisition). Use Python similarly to updating a JSON file when discarding volumes:

  d = json.load('input_fmap_file')
  d.update({'IntendedFor': new_func_files_list})
  json.dump(d, open('input_fmap_file', 'w'), indent=4)

Although this is a semi-automatic and not perfect solution, it is better than implementing it fully in a bidsmap file. First, it is more general. Second, implementing different IntendedFor values depending on the fieldmap run in a bidsmap file, requires to involve explicit subject ids and duplicate the fmap section.