Added Japanese translations. Renamed Japanese .mo file

Language files for Japanese mqTranslate V2.7.1.1 .PO file. 

Filename was changed from mqtranslate-ja_JP.po to mqTranslate-ja.po because naming convention of Japanese .MO file is XXX-ja.mo. I had reported this issue to qTranslate but was ignored ...


### Fixed screen shots

![mqtranslate-fix1](https://cloud.githubusercontent.com/assets/8876600/4431107/11a97ee2-4658-11e4-9d16-b793bab897fe.jpg)
![mqtranslate-fix2](https://cloud.githubusercontent.com/assets/8876600/4431108/19f5e874-4658-11e4-86f8-61b24dfd1553.jpg)
![mqtranslate-fix3](https://cloud.githubusercontent.com/assets/8876600/4431109/21e9b31c-4658-11e4-9402-eaebe2c6c1f1.jpg)
![mqtranslate-fix4](https://cloud.githubusercontent.com/assets/8876600/4431112/308c4f92-4658-11e4-98ab-25c9489e3f0e.jpg)
![mqtranslate-fix5](https://cloud.githubusercontent.com/assets/8876600/4431113/37d8ea8a-4658-11e4-8383-11d1e29753ae.jpg)