Charts using the same representation (vtkChartRepresentation) to manage data as
well as selection. The problem with  this approach is that whenever the
selection changes, we have to reexecute the vtkChartRepresentation even if the
data didn't change and only the selection changed. The representations in 3D
view deal with this my creating a separate SelectionRepresentation and the
selection input is fed directly to this representation. That way when the
selection changes, only the SelectionRepresentation is modified. We adopt that
same approach for chart representations.

Added a new vtkChartSelectionRepresentation. vtkChartRepresentation now creates
a vtkChartSelectionRepresentation that deals with delivering/showing selections.
vtkSIChartRepresentationProxy ensures that the vtkChartSelectionRepresentation
is set correctly on the vtkChartRepresentation; while
vtkSMChartRepresentationProxy ensures that the selection-input is set correctly
on the proxy corresponding to vtkChartSelectionRepresentation.

+ Also cleaned up AnnotationLink. Now, we consistently create AnnotationLink in
the vtkPVContextView (or subclass). In the past the link was created in
vtkChartRepresentation or vtkPVPlotMatrixView.

+ Also cleaned up vtkPVCompositeRepresentation.

During the evolution of vtkPVCompositeRepresentation, there was stage when we
were thinking of passing selection-input transparently to the
SelectionRepresentation held by vtkPVCompositeRepresentation. However, that
meant that vtkPVCompositeRepresentation would be marked as modified whenever the
selection changed. So to avoid that, we changed the code to setup the selection
input directly to the SelectionRepresentation in vtkSMPVRepresentationProxy.
The unused code persisted in vtkPVCompositeRepresentation. Removing that.

Change-Id: I1c834976c1aeb6343732a3c61fb3bd4876562ff0