Enhance FR translation

Change a few strings to clean up the view and make it look like it should (french usually needs more characters than english to express the same idea, it was not good on the Settings tab, see the screenshot)

![sans titre](https://cloud.githubusercontent.com/assets/6444179/3496600/3f4f85da-05e4-11e4-833c-e92e7987a7e4.png)