`/print` command enhancements

[auburnsummer]

• add private option which makes message ephemeral
  • note this will require refactoring as the initial ACK may also need to be ephemeral
• use difficulty words instead of number
• add style option controlling how the message is printed
  • default: current version
  • detailed: adds more fields
  • json: prints a json of the metadata
  • blend: daily blend style with message