Change color map generated by SetTreeColorArray()
Change color map generated by SetTreeColorArray()

SetTreeColorArray() now displays all edges with negative values
in shades of red, and all edges with positive values in shades
of blue.  Edges with a value of zero are now drawn in grey.

When SetTreeColorArray() is called, the edges in the tree are
now drawn slightly thicker.  This makes it easier to see the
colors.

Change-Id: Id0564e1e8d0389bcd395fdbbb3cba84ee720665c

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