[enh] Create ynh_backup helper based on ynh_bind_or_cp
[enh] Create ynh_backup helper based on ynh_bind_or_cp

YunoHost/moulinette-yunohost,YunoHost/yunohost,YunoHost/moulinette-yunohost,YunoHost/yunohost,YunoHost/moulinette-yunohost,YunoHost/yunohost,YunoHost/moulinette-yunohost,YunoHost/moulinette-yunohost,YunoHost/yunohost