Implement --terse option

Defined as suppressing logs of level INFO and below.

Altered from original '--quiet' patch with additional hacking from
Daniel Farina <daniel@heroku.com>.
Add Christophe Pettus as a contributor
Eliminate unecessary logging on restore

Tweak race error message by bumping severity to WARNING and note in the
message copy that the URI at one point existed but can no longer be
found.