Add Chinese translation

This translation was based on English version of this software.

Feel free to contact me at BM-2cWU8BgaGp2EUqzhS3QVa7umV1k2Dm4Z8c

There is a term table  available at http://kkdev.org/2014/01/07/bitmessage-term-table/ , most of them is translated by meaning , but not how it appears in English. 

Currently, It needs to modify keys.dat to switch to Chinese. 

Tested at Ubuntu 13.10 64-bit.

![screenshot from 2014-01-07 11 38 15](https://f.cloud.github.com/assets/1883569/1856326/aaae0f2a-774d-11e3-8321-5702fe866624.png)