* Overhaul for proper systemd support (LP: #1436937) * bin/oem-config-prepare: set the systemd default target to oem-config.target instead of using /var/lib/oem-config/run as a flag. * bin/oem-config-firstboot: - after removing the oem user, set the default target back to graphical. - call for systemd to start the graphical target, so as to complete booting to graphical or to TTYs after oem-config-firstboot has run. * debian/oem-config.target: create a new target for oem-config so that it can start without conflicting with a display-manager that may also want to start and use the oem user in auto-login. * debian/oem-config.oem-config.service: simplify the service's start conditions; we don't really need to worry about Before/After since we'll run in our own isolated target. * debian/oem-config.install: force the installation of the new target in the right location for systemd.