French localisation strings

[slegros]

# Create a installer with InstallForge and choose French as language
# Run the installer

*Result* :
- in the licence section, a space is missing between _règlement_ and _avant_
- in the additionnal tasks, a space is missing between _installés_ and _pendant_; there is a extra space just after the product name, just in front of the comma; also we should read _Icônes additionnelles_ (feminine).
- in the cancel installation dialog, a hyphen is missing between _Voulez_ and _vous_.