Summary of the changes:

- vtkChartRepresentation always takes composite data sets as input. If
  there is only one data set, it will create a multiblock data set.

- The data sets in vtkChartRepresentation can be selected by using the
  functions that modify the parameter
  vtkChartRepresentation::CompositeIndices

- vtkXYChartRepresentationOptions::Internals::PlotMap now maps each
  series name to multiple tables and plots (that have columns of the
  same name)

To dos:

- Selection has a bug when the input is multiblock

Change-Id: I1bf97f38e4b3866cd532048363bf638d022f5938