Migrate to Data Package v2 (once supported by frictionless-py)

[ezwelty]

Version 2 of the Data Package specification will soon be released. Once it is supported by frictionless-py (and ideally Frictionless Repository, which we currently use for some of our CI tests), we could migrate the metadata to use it. See the Changelog.

• $schema: https://datapackage.org/profiles/2.0/datapackage.json
• contributors: Replace role with roles array populated with DataCite terms (creator, DataCollector, DataCurator, possibly DataManager).
• dialect: Add type: delimited depending on outcome of Split Data Package spec into its own repo frictionlessdata/datapackage#74
• schema: Add fieldsMatched: exact
• field
  • Set pipe-delimited fields to type: list
  • Move constraints.enum to categories, where each category has a value and a description, updating documentation templates as necessary.