add new ways to destroy droplets

[rjbs]

No description provided.

[rjbs]

@lerlacher-fm Happy to merge this without review soon, but giving you a chance to look at it first. This adds things like:

box destroy --by-name this-stupid-box

If the name is ambiguous, you must supply --ip to disambiguate. This does not add the droplet id to the listing because there's not a lot of real estate in my terminal and this seemed like a good compromise. You can use the id, though. Can add it to the listing later…

[lerlacher-fm]

Thanks for adding this, looks good to me!