Upgrade to W3C VC 2.0 Data Model

[surendrasinghs]

1. Identify differences between 1.1 & 2.0 for task break-up and estimation
2. Ensure backward compatibility with W3C VC 1.1 items, esp for revocation and verification API
3. Issue all new credentials in the 2.0 data model
4. For credentials issued in 1.1 data model, do we need to provide a READ/GET response in 2.0 format?
5. Maintain two SDKs/libs/services — one in Node/TypeScript and one in JAVA? Java is yet to be created.
6. Release versioning (TBD)
7. Documentation, test coverage, performance testing, migration (TBD)