Payasan notes - notelists and eventlists

Although it's non-standard and personal, I think the idea of distinguishing between notelists and eventlists is valuable. Promoting this distinction is one of the main reasons for the current (and long) refactor of Payasan.

A notelist in Payasan is tiled - remember the slogan "no gaps, no overlaps". More widely, staff notation and "time box" drum notation are tiled music representations. Tiled representations enjoy conciseness.

An eventlist explicitly features time - the onset time and duration of events. Overlaps and gaps are inherent as events have no responsibilty to be contiguous. Csound scores and MIDI are examples, as are "track views" in digital sound editing programs.