Added GapSize option for series.

Defines when to display a gap in the graph. A gap size of 5 means that if the
distance between two points is greater than five times that of the two
closest points, the graph will be broken.
In practice, this option is most often used to visualize gaps in time series.
In a stock chart, intraday data is available for daytime hours, while
gaps will appear in nights and weekends.
Defaults to 0.