Re-Work of Simplified Chinese Translations

### Problem

Legacy simplified Chinese i18n files from OpenX 2.8 are very much buggy:

 * Most characters were corrupted when UTF-8 was introduced to OpenX.
 * Incorrect/misleading translations, like 'contract' being mistaken for 'contact'.
 * Inconsistency on term for 'advertiser'.
 * Inconsistency on file structure from the i18n files for English.

### Work I've Done

So I decided to start translating from scratch, based on the English version of files from OpenX 2.8.10.

Currently the translation work is not completed yet. Especially those for 'Administrator' role are not quite done.
But it should be sufficient for working on most daily routines as the 'Default Manager' role. (_Well, in China, technical guys usually have better English skills than the salespeople._)

I've been working with the following priorities:
 0. Daily routine pages for 'Default Manager' role
 0. Daily routine pages for 'Administrator' role
 0. Error messages for 'Default Manager' role
 0. Error messages for 'Administrator' role
 0. Installation & upgrading pages
 0. Other