Add option to disable predictable network interface naming
gummiboot-builder.py: Handle the case where there's no /etc/machine-id.

Bug hit by add^_ in IRC when installing from the livecd, as there's no /mnt/etc/machine-id
Linux 3.6 has been EOL'd, hopefully 3.7 works for the fuloong2f
Add websockify service
Fix manual build
Add a module for MiniDLNA

Now my NixOS machine can serve videos to my Bluray player!
modules/config/fonts.nix: export GDFONTPATH in /etc/profile

Set the environment variable GDFONTPATH to the list of directories where fonts
are expected to be installed. This is search path is used by same GD-based
applications, such as Gnuplot.

Alternatively, we could rely on fontconfig to achieve the same thing, i.e. by
running

  for n in $(fc-list | sed -r -e 's|^([^:]+):.*$|\1|'); do echo $(dirname "$n"); done | sort | uniq

to get that list at run-time, but the static approach feels more deterministic.
modules/config/fonts.nix: revert "export GDFONTPATH in /etc/profile"

This reverts commit 2802538dc2e2a8923e3d3cc3e144abc4e1561760. The idea
was good, but unfortunately $GDFONTPATH has a different format, i.e.
programs that use this variable don't descend into the directories
listed here like fontconfig does, so we cannot use the same values for
both settings.