patchstack/customized main

Enable greeters, starting after first-boot-complete.target

This allows a user to be created by systemd-firstboot.service, after
which the greeter can be launched.
Trying to upstream in https://github.com/systemd/particleos/pull/87

jcgl updated patch to version 3
jcgl updated patch to version 2
jcgl created patch version 1