French manuals and UI localization updates

[Jean-Pierre Chrétien]

Hello

commit 866b6d0ea33155c54b0e2efa3f8cd6759ade4429
Author: jpc <j...@lyx.org>
Date:   Wed Jul 27 18:12:06 2016 +0100

      Update French UI localization

commit 14c308749f00c94af36ac95165dee614ef0c5ce1
Author: jpc <j...@lyx.org>
Date:   Wed Jul 27 18:09:40 2016 +0100

       Update French Customization, Math, Tutorial and UserGuide manuals

Richard, ok to push ?

--
Jean-Pierre