Renamed "Aperçu" into "Mini-Preview" in visible places
Having an thing whose name requires special UTF-8 character to be properly
displayed is a source of portability problem (including xgettext issue
reported by Alwin);
Considering also that this french word is only understood (sparesely) in
Great Britain, but not by international english speaking community;
This patch then replace it by the "Mini-Preview" suggested by Yuri
Tarasievich, which is more likely to be understood.
Signed-off-by: Christophe CURIS <christophe.curis@free.fr>