--format -f options instead of --json and --csv

[russbiggs]

To make things more extendable in the future I think it would be better to switch to a --format/-f option in lieu of the --json and --csv flags. This would allow us to add more format options if needed in the future and have a more consistent API and less flags. It would also solve the issue of needing to check that the two are mutually exclusive since as we can just parse the last instance of --format