status: builtin command for system administrators


I added a command 'rpm-ostree deployment' which serves a similar function (and uses similar code) to 'ostree admin status' in that it displays the list of deployments, indicating which one is currently booted into.  I added an additional feature, however, that marks an 'r' next to the deployment that is the most recently upgraded version, because I found through several rollbacks and reboots, it was difficult to keep straight which one was most recent without querying rpm to check a package version.
The command also tells this information in plain text.
I updated the man page, both to reflect this command and to add clarifications in other sections as I saw fit.
Thanks!