add(coreos-base/oem-niftycloud): added initial oem for niftycloud

These are the initial oem scripts for niftycloud.
NIFTY Cloud is one of the most popular public cloud service in Japan.

cc: @kelseyhightower 
I find the cause of this issue. I allways put the following user-data to set DNS.

```
#cloud-config

coreos:
  units:
    - name: nameservers.network
      content: |
        [Network]
        DNS=8.8.8.8
        DNS=8.8.4.4
```

If user-data includes Network section, systemd-networkd doesn't retrieve IP.