Gracefully handle SIGTERM as well as SIGINT

the app will clean up after itself on a SIGINT, but not a SIGTERM. It should be easy to make it gracefully cleanup in both cases (i.e. stop the firewall).

i believe it is standard practice to respond and cleanup to both INT and TERM (https://en.wikipedia.org/wiki/Unix_signal)

low priority, but easy

(from redmine: created on 2014-05-12, closed on 2014-05-19)