Extra warnings for deleting jobs

[jweede]

It's a little too easy to delete jobs and wipe out build history.
We should prompt for extra confirmation when a changeset calls for deleting jobs.

• prompt for extra confirmation (force typing out "yes" like TF)
• list jobs to delete
• look scary with colors

[nerdling]

If delete is not considered normal operation for this tooling, then we shouldn't even allow deletions by default.

Perhaps this should instead be a flag that even allows deletes?

[jweede]

That sounds better. We could disable deletes normally, and only allow with a flag like --allow-delete