Add DeidentificationMethod and DeidentificationMethodCodeSequence to json

[CGSchwarzMayo]

This parallels my PR to bids-specification:
bids-standard/bids-specification#1772
bids-standard/bids-specification#1709

The goal is to add DeidentificationMethod and DeidentificationMethodCodeSequence to json, so that users downstream have a chance to be informed of whether some tags were scrubbed and/or if any de-facing or other image scrubbing was applied.

From our email discussion, I understand that you will probably not merge this until bids-specification merges theirs. I thought we could iterate on this, if needed, in the meantime.

Thanks for your consideration,
Chris Schwarz
Mayo Clinic

[neurolabusc]

The master branch is always the current stable release, and only accepts PRs from the development branch. You must make a PR to the development branch.