Fix #476 Auto language changing function finished.

Fixes issue#476.
If the user does not have the freeseer.conf file, the function will detect the system location for default language.
If there is a config file, the language setting in that file will have higher priority.
For Chinese, If the location is not zh_CN, Traditional Chinese will be used.
If there is no translation for the system location, English will be used.
Is `ja` correct?
```python
>>> from PyQt4.QtCore import QLocale
>>> QLocale(QLocale.Japanese).name()
PyQt4.QtCore.QString(u'ja_JP')
```