Added

• TrackView and SomeTrack types to libtrackerboy/data
• Song.getTrackView member proc

Changed

• Track data is stored using a ref array instead of a seq
• Each track is allocated for 256 rows, regardless of the song's trackLen parameter. This allows for changing the trackLen without losing data at the cost of extra memory consumption when trackLen < 256.

Removed

• len and setLen overloads for Track instances, use the Track.len field instead.
• trackLen and setTrackLen procs, use the Song.trackLen field instead.