BUG: Fix vtkPlotHistogram2D to render correct size
BUG: Fix vtkPlotHistogram2D to render correct size

vtkPlotHistogram2D::Paint() was rendering its vtkImageData
slightly too small.

The extent of a vtkImageData object "is defined by the index of the
first point and the index of the last point". The length should be
(last - first + 1).

Change-Id: Ieb35f362d9e909d0eadf09bc7c522ed06fbc59d1

cjh1/VTK,biddisco/VTK,daviddoria/PointGraphsPhase1,demarle/VTK,spthaolt/VTK,daviddoria/PointGraphsPhase1,collects/VTK,aashish24/VTK-old,cjh1/VTK,collects/VTK,keithroe/vtkoptix,collects/VTK,berendkleinhaneveld/VTK,jmerkow/VTK,spthaolt/VTK,aashish24/VTK-old,biddisco/VTK,ashray/VTK-EVM,SimVascular/VTK,biddisco/VTK,mspark93/VTK,hendradarwin/VTK,ashray/VTK-EVM,biddisco/VTK,msmolens/VTK,demarle/VTK,johnkit/vtk-dev,johnkit/vtk-dev,sumedhasingla/VTK,jmerkow/VTK,daviddoria/PointGraphsPhase1,biddisco/VTK,aashish24/VTK-old,sankhesh/VTK,cjh1/VTK,johnkit/vtk-dev,msmolens/VTK,johnkit/vtk-dev,gram526/VTK,daviddoria/PointGraphsPhase1,candy7393/VTK,collects/VTK,mspark93/VTK,johnkit/vtk-dev,mspark93/VTK,gram526/VTK,hendradarwin/VTK,berendkleinhaneveld/VTK,sankhesh/VTK,sumedhasingla/VTK,demarle/VTK,aashish24/VTK-old,jmerkow/VTK,demarle/VTK,msmolens/VTK,hendradarwin/VTK,sumedhasingla/VTK,sankhesh/VTK,spthaolt/VTK,sankhesh/VTK,sumedhasingla/VTK,keithroe/vtkoptix,sumedhasingla/VTK,ashray/VTK-EVM,berendkleinhaneveld/VTK,keithroe/vtkoptix,candy7393/VTK,spthaolt/VTK,collects/VTK,daviddoria/PointGraphsPhase1,mspark93/VTK,cjh1/VTK,jmerkow/VTK,msmolens/VTK,berendkleinhaneveld/VTK,msmolens/VTK,spthaolt/VTK,keithroe/vtkoptix,jmerkow/VTK,sankhesh/VTK,demarle/VTK,gram526/VTK,berendkleinhaneveld/VTK,ashray/VTK-EVM,jmerkow/VTK,hendradarwin/VTK,ashray/VTK-EVM,cjh1/VTK,msmolens/VTK,candy7393/VTK,candy7393/VTK,spthaolt/VTK,SimVascular/VTK,biddisco/VTK,sumedhasingla/VTK,hendradarwin/VTK,gram526/VTK,jmerkow/VTK,daviddoria/PointGraphsPhase1,sumedhasingla/VTK,sumedhasingla/VTK,keithroe/vtkoptix,jmerkow/VTK,ashray/VTK-EVM,hendradarwin/VTK,candy7393/VTK,candy7393/VTK,ashray/VTK-EVM,msmolens/VTK,gram526/VTK,demarle/VTK,keithroe/vtkoptix,berendkleinhaneveld/VTK,sankhesh/VTK,mspark93/VTK,mspark93/VTK,sankhesh/VTK,johnkit/vtk-dev,berendkleinhaneveld/VTK,msmolens/VTK,cjh1/VTK,gram526/VTK,demarle/VTK,keithroe/vtkoptix,SimVascular/VTK,mspark93/VTK,ashray/VTK-EVM,biddisco/VTK,candy7393/VTK,SimVascular/VTK,aashish24/VTK-old,keithroe/vtkoptix,gram526/VTK,candy7393/VTK,demarle/VTK,mspark93/VTK,hendradarwin/VTK,spthaolt/VTK,SimVascular/VTK,gram526/VTK,johnkit/vtk-dev,collects/VTK,aashish24/VTK-old,SimVascular/VTK,SimVascular/VTK,sankhesh/VTK,SimVascular/VTK