Adding Ubuntu keys from behind a firewall

Ubuntu requires a key to be installed to use a third-party apt-get source like MongoDB's packages. Unfortunately, fetching this key uses port 11371, which is blocked by lots of work firewalls.

Luckily, keyserver.ubuntu.com listens on port 80, so there's a bit of a kludgy workaround. Change 7F0CEB10 to your key identifier...