vtkTestingMacros: Temporarily remove baselines from VTKData
vtkTestingMacros: Temporarily remove baselines from VTKData

Teach vtk_add_test_* remove baseline images for each test from the
VTKData or VTKLargeData tree.  This is a temporary change meant only for
use locally to transition VTKData and VTKLargeData baseline images to
ExternalData content links.

Change-Id: I510418dd367ae01995992bfb3b9df0bb021e27da

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