Add systemd support and start updating archlinux stuff

Patch on top of pull request 15

Arch Linux switched to systemd some time ago, unfortunately rackspace
and open stack are behind. This patch provides a systemd.service unit to
be installed on Arch Linux images, it should also work for fedora and
anyone else that booted with systemd.

I just started working at rackspace last week, (A8 first shift) but I
would really like to know how I can get my hands on that Arch Linux
image that still defaults to initscripts so I can bring it up to date
and also learn more about openstack and nova-agent and the json rest
api.

I am also working on a small set of patches for the switch to netctl
since we also just dropped netcfg from the repositories to the aur
today.

https://www.archlinux.org/trustedusers/#dwallace