[STORY] Move JSON edits functionality to converter from Bids store

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Description

Post-hoc editing of JSON side cars of NIFTIX (see #92) should be handled Dicom->Nifti converter instead of part of the Bids store, because it will be needed for non-BIDS apps too.

Acceptance Criteria

When DICOM files are being converted to NIFTI format, editable arguments should be able to be passed to the converter to enable post-hoc editing of the generated JSON side cars

Notes

The edits could be stored in XNAT (potentially in a different resource of the scans to be converted ARCANA__CONVERTER_ARGS) and editable by an arcana CLI

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Epic: Australian-Imaging-Service/pipelines#33

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This has ben included as part of the fMRIPrep field maps changes