Add french translations

I hope it's complete now.

My own changes are only on the following files : 
- locale\fr-FR\treestyletab\treestyletab.dtd
- locale\fr-FR\treestyletab\treestyletab.properties

But my pull request include 2 files I did not change : 
- buildscript
- modules/base.js

I don't know what I made wrong with GitHub.