Develop bids-migration script

[yarikoptic]

Should perform necessary actions on a BIDS 1.?.? datasets to migrate them into a "proper" BIDS 2.0.0 (and/or later) dataset. Some of the actions I foresee it to do (to be modified as we go)

• rename participants.tsv to subjects.tsv . Homogenize "Subject" Nomenclature #14
• provide ... field to dataset_description.json to describe layout (could be with or without session): Make it possible to specify folders layout to be other than sub-{label}/[ses-{label}/] #54

while working on those we should test it

• tested on https://github.com/bids-standard/bids-examples .
  • Should use new dyno based validator against the modified schema from BIDS 2.0 PR
  • Valid bids 1.x datasets should remain valid bids 2.x after migration.
  • should be integrated with bids-examples repo to carry bids-2.0 branch which gets updated by converting all examples into BIDS 2.0 specification. To be triggered when migration script changes (could be done from workflow here triggering a workflow there), or when bids-examples master branch changes

[yarikoptic]

it is being developed as part of the

• https://github.com/bids-standard/bids-specification/pull/1775/files#diff-24b8a97543a1dc43190b8d5b070df26e1b88023f2b468b4483255af049788788