[Fedora-spins] Integrating Spins and systemd for f17

[Bruno Wolff III]

Adam Williamson has a patch for changing live images to replace some usage
of sysvinit with systemd in https://bugzilla.redhat.com/show_bug.cgi?id=739446 .

This is a significant change that people should be thinking about. We really
should be moving in the direction of using less sysvinit and more systemd
going forward.

At first glance I don't like the creation of supporting files for each
spin, but it may end up being the best way to do this.

It would be nice if people interested in live images would critique the
ideas in the patch and suggest improvements or alternatives for moving
toward replacing sysvinit with systemd.