add localisation

The GUI files are modified so that they can be translated in other languages.

__init__.py modified to use the user system locale.

New folder : translations/, where translations are stored (actually only french). 

![Uploading Capture du 2013-06-12 10:54:22.png . . .]()
![Uploading Capture du 2013-06-12 10:53:58.png . . .]()