[Systems] Lightwave is now running Ubuntu 18.04

[Bernie Innocenti]

All I had to do is run do-release-upgrade and merge a few config files
with local edits.

After the upgrade, the network wasn't coming up, so I logged in from the
console and figured out that the pre-systemd legacy network
configuration was disabled because  had unsinstalled the required
support. The quick fix was:

  apt install ifupdown

Anyone more familiar than me with systemd-networkd is welcome to migrate
lightwave to the new config, but please verify that the tun6to4
interface still works: we host several domains with IPv6 nameservers,
like the big guys :-)

-- 
 _ // Bernie Innocenti
 \X/  https://codewiz.org/