[arch-releng] [RFC] [archiso] Use a pure systemd enviroment

[Gerardo Exequiel Pozzi]

* rewrite automatic_script to work with systemd or completelly in automatic 
login shell.
* research how to avoid systemd to stop archiso mounted filesystem and leave 
all the work
  to our special shutdown script in initramfs
  (just works, but shows lots of resource busy at shutdown)