this fixes #67

archiso specific options are placed in a /etc/systemd/system/reflector.service.d/archiso.conf drop-in.

reflector.service will update pacman's mirrorlist after a network connection is established in the live system.
Fixes #26 .

configs/releng/airootfs/etc/systemd/system/multi-user.target.wants/iwd.service:
Adding a symlink to /usr/lib/systemd/system/iwd.service to enable iwd in
airootfs (and thus on the image).

Closes #18