Use default translation file for french locales.

As 'fr_FR' and 'fr_CA' locale files are identical, use only one default 'fr' file.
It also allows other french locales (fr_BE, fr_CH, etc...) to have the french translations without having to duplicate the file for every locale.
Update locale files to add the new strings.
Merge pull request #33 from glv2/locale-fr

Use default translation file for french locales.