3486 quiet cmds

Fixes #3486.

I added -q/--quiet CLI args to push and pull, and ?q=1 API query params to /images/(name)/push and /images/create, both modelled after the docker build args.  All it does is set the job's Stdout to a NopWriter if the parameter is found.  I'm not sure if this is the best way to handle suppressing output, but it seems to work just fine.

I didn't add any tests because I didn't see any similar existing tests, and this seemed too minor a change to warrant adding major CLI/API testing code.  I tested with pull and it seems to work just fine, including the exit code.  Sometime soon I'll test pushing on a private repo, when I get that set up.