Switch language name 'zh' to 'zh-cn'

This is the first step to rename 'zh' to 'zh-cn'. There are several reasons why we rename the language name.

- The upstream docsy theme changed the language name, leading to many warnings during site build;
  The side-effect is that the i18n strings are no longer working.
- We believe renaming the language is the right thing to do, because this move can make room for other variants of Chinese language, such as 'zh-tw', 'zh-sg' etc.

There would be several follow-ups to this PR, such as fixing the intra-site links, adding redirects etc.

We will lock up changes to zh/zh-cn pages for the moment, until this one gets in.

This PR is based on commit cdad0a7342.

content/zh-cn/docs/reference/glossary/configmap.md

@@ -0,0 +1,44 @@
+---
+title: ConfigMap
+id: configmap
+date: 2018-04-12
+full_link: /zh/docs/tasks/configure-pod-container/configure-pod-configmap/
+short_description: >
+  ConfigMap 是一种 API 对象，用来将非机密性的数据保存到键值对中。使用时可以用作环境变量、命令行参数或者存储卷中的配置文件。
+   
+aka: 
+tags:
+- core-object
+---
+
+<!--
+---
+title: ConfigMap
+id: configmap
+date: 2018-04-12
+full_link: /docs/concepts/configuration/configmap/
+short_description: >
+  An API object used to store non-confidential data in key-value pairs. Can be consumed as environment variables, command-line arguments, or configuration files in a volume.
+
+aka: 
+tags:
+- core-object
+---
+-->
+
+<!--
+ An API object used to store non-confidential data in key-value pairs.
+{{< glossary_tooltip text="Pods" term_id="pod" >}} can consume ConfigMaps as
+environment variables, command-line arguments, or as configuration files in a
+{{< glossary_tooltip text="volume" term_id="volume" >}}.
+-->
+
+ ConfigMap 是一种 API 对象，用来将非机密性的数据保存到键值对中。使用时， {{< glossary_tooltip text="Pods" term_id="pod" >}} 可以将其用作环境变量、命令行参数或者存储卷中的配置文件。
+
+<!--more--> 
+
+<!--
+A ConfigMap allows you to decouple environment-specific configuration from your {{< glossary_tooltip text="container images" term_id="image" >}}, so that your applications are easily portable.
+-->
+
+ConfigMap 将你的环境配置信息和 {{< glossary_tooltip text="容器镜像" term_id="image" >}} 解耦，便于应用配置的修改。