GitLab

* Set autoupdate default to lab computers
* Create a new sub-group for the lab, so that one can handle their
  specific behaviour more easily (see
https://docs.ansible.com/ansible/latest/user_guide/intro_inventory.html#inheriting-variable-values-group-variables-for-groups-of-groups )

* The handler set the network down and then set the same network up
  again and not the new KITnet. So if the old network was not KITnet
(which is the case on newly installed machines or any machine that
hasn't been merged manually).
  Now KITnet is started.

* Set the environment varible for EPICS IOCs depending on the environment
  (meant for KARA, LASMagLab or TGU)
  * Use groups and vars in host file to manage these different cases
* Fix problems with the DHCPd role
  * host lists were at wrong location (may be this can be improved)
  * one should check explicitly for variable names (linter warning)

* Use git submodule to have to update the scripts at one place only
* Change the path in the role and delete the old script

Seems to be a malfunctioning NetworkManager's DHCP own client, see
https://bbs.archlinux.org/viewtopic.php?id=252265 and
https://wiki.archlinux.org/index.php/NetworkManager#DHCP_client

* Add nm-settings-ifcfg-rh files
* Add IPv6 stable secret
Fixes issue #91

* Anaconda (Fedora's installation routine) may/should create a file to
  allow root login at the very first reboot. This file should be deleted
after properly SSHd configuration.