Find a VTK installation or build tree.

The following variables are set if VTK is found. If VTK is not found, VTK_FOUND is set to false.

VTK_FOUND         - Set to true when VTK is found.
VTK_USE_FILE      - CMake file to use VTK.
VTK_MAJOR_VERSION - The VTK major version number.
VTK_MINOR_VERSION - The VTK minor version number
                     (odd non-release).
VTK_BUILD_VERSION - The VTK patch level
                     (meaningless for odd minor).
VTK_INCLUDE_DIRS  - Include directories for VTK
VTK_LIBRARY_DIRS  - Link directories for VTK libraries
VTK_KITS          - List of VTK kits, in CAPS
                    (COMMON,IO,) etc.
VTK_LANGUAGES     - List of wrapped languages, in CAPS
                    (TCL, PYHTON,) etc.

The following cache entries must be set by the user to locate VTK:

VTK_DIR  - The directory containing VTKConfig.cmake.
           This is either the root of the build tree,
           or the lib/vtk directory.  This is the
           only cache entry.

The following variables are set for backward compatibility and should not be used in new code:

USE_VTK_FILE - The full path to the UseVTK.cmake file.
               This is provided for backward
               compatibility.  Use VTK_USE_FILE