Fix issue #35, arpeggiator notes in wrong order

Fix bug introduced in ae61cd9bd315642cd45409eeb9daae8e08ca50c3 causing notes above note 40 (counted from the bottom C on the keyboard) in up/down mode to be arpeggiated in the wrong order, due to overlap in the arp.notes vector (the vector must be long enough to fit the note range seen by the arpeggiator twice in this mode).

This is done by reverting the note range to 0..60 internally within the arpeggiator. Another potential solution would be to extend the arp.notes vector.