allow prepSelect callers to set own fillRangeItems routine
allow prepSelect callers to set own fillRangeItems routine

- e.g. to allow mapbox subplot convert px coords to lon/lat
  w/o hackely mocking too many things

plotly/plotly.js,iongroup/plotly.js,etpinard/plotly.js,aburato/plotly.js,asolagmbh/plotly.js,iongroup/plotly.js,iongroup/plotly.js,plotly/plotly.js,asolagmbh/plotly.js,aburato/plotly.js,plotly/plotly.js,etpinard/plotly.js,plotly/plotly.js,etpinard/plotly.js,asolagmbh/plotly.js