Update BWV988 v19

update to LilyPond v2.18.2
Bar 9: treble top voice, replace slur with tie on fis4
Bar13: treble top voice, add tie to c8
Bar17: middle voice, add tie to d4
Add cautionary accidentals
Adjust beams, ties, staff placements
Set midi tempo
(Javier Ruiz-Alma)
Close #100