Also check forbidden/unknown licenses for save, csv commands

[Bobgy]

I think it doesn't make sense to successfully terminate save/csv commands when there are forbidden licenses.

Also, it'd be time wasting if we run the check command and save/csv command together, because with the current implementation, we will need to re-scan for all licenses again.

Proposal

Two options:

• breaking change: let save/csv commands check license type as well and emit errors if any problems are found
• backwards compatible: add a new flag like --exit_status or --check, and also do the check logic in other commands as well

[wlynch]

I think the --check option makes the most sense here. We can keep the existing behavior (which seems useful as a standalone reporting tool).