Add --quiet flag

[nfg]

Hey! This popped into my head as a potential feature. It lets me run cpm like

👾  test-project git:(master) ✗ cpm install --quiet
32 distributions installed.

I pretty much copied the existing logic for --verbose. It's pretty trivial, so no worries if you're not interested.

Thanks for your work! Discovering cpm many years ago greatly changed how I approach managing dependencies. Cheers :)