OpenTURNS integration

This commits adds multiple OpenTURNS related features, including

• A new PARAVIEW_USE_OPENTURNS cmake option to turn on to use these features
• A dedicated xml to expose the new some OpenTURNS filter proxys
• An extension to the PlotMatrixView for displaying Density Maps
• vtkPVHistogramView changes to support the display the outpout of OpenTURNS filters
• vtkPVPlotMatrixRepresentation changes to support OpenTURNS features
• Update to vtkPVHistogramRepresentation to handle CenterBinAndAroundMax
• Changes in PlotMatrixRepresentation default values to improve its look and feel
• Modifications in Chart Management to automatically display line chart in the correct corner
• Adding a ShowOneRepresentationAtATime XML view proxy hint
• Adding/Updating related tests