French translation by Joseph Gastelais, and some French and German translations for the desktop files
Add French translation created by Joseph Gastelais a.k.a Joe Linux (https://www.linuxrouen.fr), thanks Joe! While we're at it, also added French desktop menu item translations by Olivier Humbert (via https://github.com/agraef/purr-data/pull/8, thanks Olivier!), and German menu item translations by yours truly.