Filter containers by status.

A continuation of #7616.
Closes #7616.
Adds `docker ps --filter=status=(restarting|running|paused|exited)` option.

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)
Yes, what Jessie said. Ideally we would be consistent everywhere and use "ID", but in code comments I'm willing to let things slide a little just because it would be a disproportionately large effort to enforce things everywhere and relatively few users are exposed to these docs (and the ones that are have a different set of expectations than they do for "actual" docs).