Better gracenote playback

[macarc]

If all gracenotes also came with a 'timing' - a list of numbers representing how long each note is when played - then playback would be more realistic (since usually the notes in a gracenote are not all the same length).

I supposed that a GracenoteFn should just return two arrays instead of one - that's easier than having two separate functions with the same conditional logic

[DavidGriffith]

Perhaps related: as speed goes up, the gracenotes start sounding unnaturally blurred together.

[DavidGriffith]

Another perhaps related: I imported a BWW file of "The Dark Isle", which was converted from BWW format as told by the line "Converted from BMW Dos file format to Bagpipe Reader 1.0 format using BMWFC32.". I had to turn the tempo down to 30 to make the regular notes sound right. But then the gracenotes were all slowed down to where they sounded almost like eighths notes.