feat(app-emulation/google-startup-scripts): initial commit
feat(coreos-base/oem-gce): add google-startup-scripts
feat(coreos-base/oem-gce): add the gce-add-metadata-host service

One of the requirements of GCE is setting up the metadata host. Do this.
fix(coreos-base/oem-gce): make gce's cloudinit oneshot