Update strings.js of zh-cn

Add Simplified Chinese translation to strings.js. Based on the file in
sprint 35 dev build.
Fix a wrong word
Merge branch 'master' into loc/chinese-sprint35
Change 2012 to 2013
Revised edition
Adjust one string
Merge pull request #6264 from gncy2013/loc/chinese-sprint35

Update strings.js of zh-cn (recreate pull request to release)