message: cmake cleanups
diff: ospray_create_library(ospray_tfn tfn_lib.cpp LINK ${OSPRAY_LIBRARIES})
  -option(OSPRAY_APPS_PARAVIEW_TFN_CVT
  +option(BUILD_PARAVIEW_TFN_CVT
  "Build ParaView to OSPRay viewer transfer function converter"
  - ON
  + OFF
  )
  -if (OSPRAY_APPS_PARAVIEW_TFN_CVT)
  +if (BUILD_PARAVIEW_TFN_CVT)
  ospray_create_application(ospCvtParaViewTfcn
  convertParaViewTfcn.cpp
  jsoncpp.cpp
  