French translation v.1.2

Here we go. Small change to the french translation:

«Cryptage» has no sense. Changed to «chiffrement.» 
In french, upcase letters have accents. Changed some A to À. https://fr.wikipedia.org/wiki/Majuscules#L.E2.80.99accentuation_des_capitales_et_des_majuscules
Other minor changes.