Since the binary name is now hidden away in /usr/lib/ the primary user
handle for the udev service is the unit name, hence change the man page
to be available under the unit name, and make the binary name an alias
for it.
This should help making the boot process a bit easier to explore and
understand for the administrator. The simple idea is that "systemctl
status" now shows a link to documentation alongside the other status and
decriptionary information of a service.
This patch adds the necessary fields to all our shipped units if we have
proper documentation for them.
