Refactored axis.getSeriesExtremes method
Cache stacked points' min / max
Correct encoding in pointer.js
Fix the problem when stacked series doesn't have negative points
Fix some issues related to refactoring stacking
- Don't call processData twice for stacked series
- Don't calculate xData min/max, it's unnecessary now
- Use Series.getExtremes to retrieve series' extremes
Fix a bug when processData throwed error on fakeSeries
Call processData just once, use not processed data to generate stacks, share cropping logic with series.getExtremes
Code lint, remove console.logs
Call Series.setStackedPoints right after processData
Calculate sums only for visible stacks
Improved logic for searching dataMin and dataMax, fixes issues related to range and OHLC series
Merge rambera branch into stacking
Remove unnecessary piece of code
Merge branch 'rambera' into stacking
Fixed rendering of flags located below data series

Previously if the label was below its data point, the connecting line was drawn over the label's text.
Now the connecting line will start from the top of the label in this case.
Don't extend Axis.getSeriesExtremes method. Extremes for waterfall are now handled by stacks extremes.
Calculate extremes for negative stacks properly
Fix error thrown after calling chart.redraw() on stacked chart
Remove unnecessary global variables
Optimize WaterfallSeries, now it uses Axis.stacks points in calculations