Update BWV-988 v24

bar12: "a" tie
bar17: remove double ties from 'a'
bar24: remove double ties from bass e
bar29: 2nd voice: d->dis
bar28: the first and second top voice d's, remove ties
(Steve Shorter)
update to v2.16.1
fix direction of ties, slurs, stems, beam angles
adjust position of rests
merge noteheads
adjust voices to staff positions according to source
remove unterminated ties
update instrument header
bar18: remove redundant 'dis'
(Javier Ruiz-Alma)
Close #56