Fix error: json export is NIST v2, not NIST v1

[sfsinger19103]

• UserGuide
• README
• Journal of Open Source Software paper
• Dataverse

(see https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.1500-100r2.pdf)

[sfsinger19103]

New version of JOSS article is in joss-submission-updated branch; as of today, this has not been communicated to JOSS, but since the issue is addressed in the repo we're going to check the box.

[sfsinger19103]

UserGuide and README are corrected in feature-2.0.1 branch.