CLI format flag over 'pretty' option

[asonnenschein]

Problem
The CLI does not currently support pretty printing JSON outputs from commands. This is annoying because JSON can be difficult to read when it's not pretty printed, and users will need to pipe CLI outputs to custom bash commands to pretty print their JSON. Supporting pretty print as an optional argument in the CLI will be a better UX.

Solution
Enhance the CLI with an optional argument to pretty print JSON outputs to stdout.

A/C

• CLI supports a new optional argument to pretty print JSON outputs to stdout for all APIs.

[ischneider]

Based on the original idea, I think it would be more like:

• introduce output option (similar to kubectl) that supports various output formats
• start with json, json-pretty (what pretty does now), ndjson (new-line delimited), flat-json
• remove --pretty (or maybe alias it to format=json-pretty?)

One question is to make it a "root" option (precedes sub-command), e.g. planet --output=json command --command-option=foo or as a command option. Personally, I prefer the latter...