Fix naming of fragment-generated normals and fix color/normal mode

Some render passes (e.g. vtkSSAOPass) assumes existence of normalVCVSOutput variable.
When there's no normal provided by the dataset, the low-memory polydata mapper generates normals in screen-space, but the naming is different.
This MR renames the local variable primitiveNormal to normalVCVSOutput.

Moreover, a second commit takes care of updating color/normal mode in the shader update, because they can be outdated if the mapper detects the shader needs to be compiled before we check for color/normal mode change.