Add onBarClick functionality to bar charts

[skolson]

Pie/Donut charts have an optional onSliceClick lambda for supporting custom actions as a result of a slice being clicked. This issue is an enhancement to provide similar functionality onBarClick for BarChart, GroupBarChart, HorizontalBarChart, VerticalBarChart, and StackedBarChart.
One example use case is to support navigating to another screen based on the bar clicked.
The solution will likely affect BarPlotData selectionHighlightData functionality if both features are coded on the same chart, as both rely on the same click action. Comments on how that should be handled are welcome.