Added a new flag 'configure_without_carrier' which will tell
systemd-networkd to configure the device even if no carrier found.

Furthermore the template will accept the absence of ipv{4,6} and
gateway{4,6}.

Note the jinjia comments "{# Keep the line below empty! #}".
If there is no empty line below this comment the templating will fail.
This will result in templating all device configs into a single file.

TODO: Make subnet configurables.
Muckefuck will have a 192.168.1.0/24 ip for communication with the hdmi
switch. Currently all ips for hosts in group "fachschaft" will be added.
So we limit that to the subnet 131.234.0.0/16.

This reverts commit 0cb95ce3.
NFS shares are available again, so this commit is not necessary anymore.

Also add nginx_main_domain variable.

This reverts commit 4ff23f4c and changes fsmi-website-tests's firewall parameters.

This reverts commit 4ff23f4c and fixes guarana's firewall parameters.

This package is mandatory to initialize the wifi devices on our ztoc
zboxes. An installtation at bootstrap time would lead to an extra reboot
step to initialize the device after the drivers are present.
Therefore I guess it is reasonable to add this package by default.