zh_CN/*.lang.php re-worked

The legacy simplified Chinese i18n files from OpenX 2.8 were very much buggy.
These files are translated based on the latest version of en/*.lang.php, and saved with utf-8 encoding.
This is still an imcomplete version. But it is sufficient for working on most daily routines as the 'Default Manager' role.
Merge pull request #135 from leesah/zh-cn

Re-Work of Simplified Chinese Translations