CLI refactor

[clehner]

In #259 a key subcommand was added with generate as a sub-subcommand (e.g. didkit key generate ed25519). Would it be useful to similarly group other commands?

Existing subcommands for DID-related functionality:

• did-auth (generate DIDAuth VP)
• did-resolve (DID -> DID document)
• did-dereference (DID URL -> data)
• key-to-did (JWK -> DID)
• key-to-verification-method (JWK -> DID URL)

Subcommands proposed in #255:

• did-create
• did-update
  • set-verification-method
  • set-service
  • remove-service
  • remove-verification-method
• did-recover
• did-deactivate
• did-from-tx
• did-submit-tx

The above proposed DID operation subcommands don't directly perform the operation (at least for did:ion) but instead return an object ("DID method transaction") which then must be passed to either the did-submit subcommand to submit it, or to the did-from-tx subcommand to derive/extract a DID from it. Maybe these operation commands should be under a operation subcommand?
Like how the the ION CLI (https://github.com/decentralized-identity/ion/blob/d644bc78b199adc07a6ade8a0774408cfb564619/cli.md#create-operation) has ion operation <create|update|recover|deactivate> [options] (although it only implements create currently).

Subcommands for VC API:

• vc-issue-credential
• vc-issue-presentation (maybe should be renamed to prove-credential, present-credential, or create-presentation, rather than impliying that presentations are issued)
• vc-verify-credential
• vc-verify-presentation

Other miscellaneous commands:

• help (built-in)
• ssh-pk-to-jwk (could be under key?)
• to-rdf-urdna2015 (could be under jsonld or ld?)

Other CLIs to consider for inspiration and/or alignment:

• did-cli
  • generate. has option to register immediately.
  • register. signs and submits an operation.
  • info - view a DID, including a local/unregistered DID
• algoid https://github.com/algorandfoundation/did-algo/blob/405fc71f691f81340c909208b6b1a52e5e0b57cf/TUTORIAL.md#2-basic-usage
  • create - algoid create <local-alias> (stateful)
  • edit - similar to didkit did-update
  • resolve - similar to didkit did-resolve. alias: retrieve and get
  • publish - creates and submits a signed operation. alias: sync, publish, update, upload, push
  • delete
• JWS-Test-Suite (VC/VP create and verify) test drivers
  • credential create -i credential.json -o vc.json -k key.jsonld
  • credential verify -i vc.json -o result.json
  • presentation create -i presentation.json -o vp.jsonld -k key.jsonld
  • presentation verify -i vp.json -o result.json
• vc-test-suite drivers: generate, generate-presentation
• Others?