Various minor changes from testing
Drilldown module, first commit
Fixed world-map demo to use the data module
Remove unnecessary piece of code
Merge branch 'rambera' into stacking
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