Features:

- introduces new Command and Route traits for Leo commands and Aleo PM API
- most of the CLI code replace with higher-level abstraction - StructOpt
- anyhow used for error handling, no more custom error classes
- improves API - now every status code has its business logic
- adds global flags (e.g. --quiet to suppress output)
- error messages improved for convenience and better user experience

Closes:

- #604
- #599
- #584
- #277
- #376

- fixes import ordering (with rule group_imports)
- removes explicit 0group from pedersen hash example
- updater is now fully-anyhow-ed :)
- fixed doc comment in prove command
- renamed cmd to command in main

- leo new/init now don't have --lib flag
- imports sorted
- command descriptions match old ones 1-to-1