Migrate a 1.3 configuration to the new configuration format

The rewrite changes the configuration (new keys, obsolete ones such as MAX_PERM_SIZE or the OpenOffice options) and replaces the init script and cron entries with systemd units. Provide a command that converts /etc/xinit/xinit.cfg, lists what could not be converted, and disables the 1.3 init script and cron entries.