Add verbosity level

[Mirek]

Would be nice for debugging, if we'd be able to enable POST body in access log. Usage can be either to change --verbose to accept parameter with verbosity level (with backward-compatible fallback to current behavior if no level is provided), or when the --verbose flag is provided twice.

[Ludovic Fernandez]

Hello,

We don't plan to manage log levels, whoami is a simple tool that focuses on simple network information.