Dcm2niix example : allowing BIDS validation of provenance records

[bclenet]

In this dcm2niix based example, we write provenance records inside the following files:

prov/
├── prov-dcm2niix_act.json
├── prov-dcm2niix_ent.json
├── prov-dcm2niix_env.json
└── prov-dcm2niix_soft.json

as well as inside JSON sidecars.

Provenance records are JSON objects inside tables so they can be encoded in the BIDS schema, and thus validated.