add cluster version info

[hao1939]

resolve #2498 .

Implementation. Store the ‘version info’ as raw string in the files:
/PAI_CODE_ROOT/
/version
PAI.VERSION
K8S.VERSION

The format would be ‘v0.12.0’ and ‘V0.12.0-1.9.9’.

There are 4 places where would need ‘version info’:

1. [TODO] It will in another PR. Webportal. It will need to display the ‘version info’ on the page, generate from the ‘version info’ during the image building process.
2. Quick-start. It will need to generate the ‘image tag’, reading the ‘version info’ on the fly.
3. Dev-box, reading the ‘version info’ on the fly. When dev-box version is not the same as the cluster, would print a warning message.
4. Build. NOTICE, not using the ‘version info’ , it will read from user config.

[coveralls]

Coverage remained the same at 52.932% when pulling ef577a6 on hao/add-cluster-info into 07e4e5f on master.

[ydye]

kubernetes-configuration.yaml has this information.

[hao1939]

There is slight difference: the k8s version is our 'customized k8s' version.
For example: v0.11.0-1.9.9 may different from v0.12.0-1.9.9, although they both base on the k8s 1.9.9.

What's your suggestion about the version string schema?

[ydye]

Remove K8S version

[hao1939]

My consideration is to make it different from PAI version, they would be decoupled later.