principally, CalendarCol.adjust(), which makes CalendarCells representing whatever's visible, and gives them tops and bottoms as appropriate.
gonna move this over to the calendar branch

Revert "principally, CalendarCol.adjust(), which makes CalendarCells representing whatever's visible, and gives them tops and bottoms as appropriate."

This reverts commit 50019d3c91f8acda419b0cd9ef90fa2059099b7a.