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/name.md

@@ -0,0 +1,41 @@
+---
+title: 名称（Name）
+id: name
+date: 2018-04-12
+full_link: /zh/docs/concepts/overview/working-with-objects/names/
+short_description: >
+  客户端提供的字符串，用来指代资源 URL 中的对象，如 `/api/v1/pods/some-name`。
+
+aka: 
+tags:
+- fundamental
+---
+
+<!--
+---
+title: Name
+id: name
+date: 2018-04-12
+full_link: /docs/concepts/overview/working-with-objects/names/
+short_description: >
+  A client-provided string that refers to an object in a resource URL, such as `/api/v1/pods/some-name`.
+
+aka: 
+tags:
+- fundamental
+---
+-->
+
+<!--
+ A client-provided string that refers to an object in a resource URL, such as `/api/v1/pods/some-name`.
+-->
+
+客户端提供的字符串，引用资源 url 中的对象，如`/api/v1/pods/some name`。
+
+<!--more--> 
+
+<!--
+Only one object of a given kind can have a given name at a time. However, if you delete the object, you can make a new object with the same name.
+-->
+
+某一时刻，只能有一个给定类型的对象具有给定的名称。但是，如果删除该对象，则可以创建同名的新对象。