datacenter config: add missing language codes and comment all

datacenter config: add missing language codes and comment all

Croatian, Georgian, Ukrainian were all added only recently, so add
them to this map here.

Arabic, Korean and Dutch was missing too, and we had those in since
quite a while.

While at it, comment the long form for every language.

Copied over from widget-toolkit's language_map, then transformed with
some vim sed foo.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>