Z:gnu-lilypond--4a0a0d-Remove obsolete engravers/tran/de

Entferne obsolete Engraver/Translatoren: Note_swallow_translator, Rest_swallow_translator, Skip_event_swallow_translator, Swallow_engraver, Swallow_performer und String_number_engraver. Neue vertikale Abstandsvariablen.