Allow salt-key -a/-r to work on rejected/accepted keys

PLEASE HOLD OFF ON MERGING UNTIL THIS PULL REQUEST HAS BEEN DISCUSSED. SEE COMMENTS BELOW FOR DETAILS.

This commit modifies salt-key so that -a looks at rejected keys in
addition to pending keys, and -r looks at accepted keys in addition to
pending keys.

The -A and -R arguments still operate on pending keys only.

In addition, this commit improves reporting on the CLI when keys are
rejected and deleted.