i18n & l10n update : updated PO strings, fr_FR localized texts

PO strings updated : from 2960 strings now on transifex to 4742 strings
+ check for en_US/messages.po : no translation inside
+ check for es_ES : removed fuzzy marker
+ check for de_DE : removed fuzzy marker

Signed-off-by: gautiermichelin <gm@ideesculture.com>