Update Locale.fr-FR.xaml

Those are very minor errors, probably from the translator's inattention. Nonetheless, some of these looked very obvious.

This is my first time with Github. I'm not used to how it works (the interface is particularly loaded and confusing at first), so I did all I could in order to clearly explain the changes I'm requesting.

Hopefully I won't have wasted my time helping to translate this, and I appologize if it's hard to read. I might check the typos some more if I have time to.
I disagree. Softwares don't talk to the user. In Help files they do but NOT on interfaces. Check the Windows 8 ribbon in french: the infinitive is used everywhere (even in tooltips).