Add support for French Language

Some users may need a French version of the ressource bundle. I attached a preliminary translation that France Labs made some time ago (probably around summer 2016), but that we halted due to lack of time (and priority). It is probably almost complete, but some quality checking needs to be done. Note also that I forgot to check the version when I did the translations, so anyone interested would need to check any modifications that may have occurred between this version and the current MCF version.