Set minimal nixos profile for our grid machines

Refs #88
Obsoletes !325 (closed)

This is a more easy way towards #88: Install less unneeded software. It sets the "minimal" NixOs profile for all our grid machines:

This profile defines a small NixOS configuration. It does not contain any graphical stuff. It’s a very short file that enables noXlibs, sets i18n.supportedLocales to only support the user-selected locale, disables packages’ documentation, and disables sound.

See this comment for more info.

nix store diff-closures

acl: -151.0 KiB
attr: -81.2 KiB
bash-interactive: -2433.9 KiB
bind: -102.2 KiB
boehm-gc: -298.7 KiB
borgbackup: -7212.5 KiB
bzip2: -12.0 KiB
command-not: ε → ∅
coreutils: -943.3 KiB
cryptsetup: -36.1 KiB
curl: -52.8 KiB
dbus: -631.0 KiB
diffutils: -215.8 KiB
e2fsprogs: -101.0 KiB
etc-man_db.conf: ε → ∅
fc: 00-nixos-cache.conf, 10-nixos-rendering.conf, 52-nixos-default-fonts.conf, 53-nixos-reject-type1.conf, 53-no-bitmaps.conf, ε → ∅, -8.3 KiB
findutils: -387.6 KiB
fontconfig: ε → ∅, -202.6 KiB
gawk: -2006.9 KiB
glibc-locales: -216977.9 KiB
gnugrep: -125.7 KiB
gnused: -198.6 KiB
gnutar: -637.9 KiB
gpm: 1.20.7 → ∅, -523.4 KiB
groff: 1.22.4 → ∅, -8284.4 KiB
gzip: -61.1 KiB
initrd-linux: +30.8 KiB
libcap: -59.7 KiB
libpipeline: 1.5.3 → ∅, -121.8 KiB
libressl: -1301.6 KiB
linux-pam: -266.8 KiB
lvm2: -285.8 KiB
man-db: 2.9.4 → ∅, -1891.3 KiB
nano: -74.6 KiB
ncurses: -637.2 KiB
nfs-utils: -92.9 KiB
nix: -763.8 KiB
nixos: -5032.4 KiB
nixos-manual: ε → ∅, -14210.2 KiB
nixos-manual.desktop: ε → ∅
perl: -140.3 KiB
perl5.34.0-DBD-SQLite: 1.66 → ∅, -400.3 KiB
perl5.34.0-DBI: 1.643 → ∅, -1738.2 KiB
perl5.34.0-String-ShellQuote: 1.04 → ∅, -16.3 KiB
shadow: -771.6 KiB
stage: +19.3 KiB
system: -14067.8 KiB
systemd: -1327.7 KiB
texinfo-interactive: 6.8 → ∅, -10364.6 KiB
util-linux: -324.3 KiB
w3m: 0.5.3+git20190105 → ∅, -1731.9 KiB
wireguard-tools: -8.8 KiB
xauth: 1.1 → ∅, -60.1 KiB
xz: -233.3 KiB
zstd: -11.8 KiB