Update Bach BWV-988 v30

bar8: treble clef, second voice beat 3.5 "a8"->"g8"; rythm not correct.
bar11: treble clef, top voice last note f->fis
bar14: treble clef, second voice first beat should be "c8. d16" not "c8 d8"
bar15: bass clef, top voice, beat 4 fis->e
(Steve Shorter)
update to v2.16.1
Treble: Add explicit 3rd voice
Adjust beaming, stem length, rest positions
(Javier Ruiz-Alma)
Close #90