ui: vocabulary: fix slider/placeholder; wording

commit d191b8f3efb6b42694e873deb60dd1f808e7fbfb
Author: Max F. Albrecht <1@178.is>
Date:   Wed Jun 25 11:33:45 2014 +0200

    adjust text

commit 7753dfd9a17336e8501aa32312b895b8522992d8
Author: Max F. Albrecht <1@178.is>
Date:   Wed Jun 25 11:33:35 2014 +0200

    refactor/fix the placeholder handling