support k8s demo (Imagenet)

[bjjwwang]

添加了imagenet的K8S的支持

1. 修改了中英文README，增加了对imagenet k8s应用的描述
2. 添加了K8S的yaml配置，
   • 采用最新的serving容器镜像
   • 用paddle serving app包来下载imagenet模型
   • 在容器中启动RPC服务
   • 暴露9696端口给外部服务

[CLAassistant]

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2 out of 3 committers have signed the CLA.

✅ suoych
✅ bjjwwang
❌ root

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