Renames and documents EXTGrid conversion methods.
Moves +makeHighlightPathAtPoint:onGrid:onPage:locClass: from EXTTerm and EXTDifferential to EXTChartViewController, which now implements the EXTChartViewDelegate’s method -chartView:highlightPathAtLocation:. Since EXTChartViewController is now responsible for building the highlight path, -[EXTChartViewDelegate indexClassForChartView:] is no more.
EXTLocation, EXTPair and EXTTriple’s followDifflForDisplay: do not declare a spacing parameter anymore. The method receives a grid location and returns another grid location. EXTChartViewController is responsible for mapping any grid locations to the view coordinate space.
Resets the highlight path in EXTChartViewController regardless of mouse event location, so resetting can be used in non-mouse-event situations. Highlight paths are only stroked if their bounding rectangles need to be drawn. EXTChartViewController now receives a grid location when asked to build a highlight path.