STYLE: improve comments and organize internal classes
STYLE: improve comments and organize internal classes

Change-Id: I8e06a64502af9f826866515f3b485d9e920eb694

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