Note that testing for VTK_BINARY_DIR or Module_WikiExamples are equivalent
since both evaluate to True when building the module from within VTK.

Report message are like the following:

```
-- VTKWikiExamples: Building VTKWikiExamples stand-alone
-- VTKWikiExamples: Building VTKWikiExamples stand-alone - yes
-- VTKWikiExamples: Setting executables prefix
-- VTKWikiExamples: Setting executables prefix - no
-- VTKWikiExamples: VTK VERSION: 8.1.0(OpenGL2)
[...]
```

or

```
[...]
-- VTKWikiExamples: Building VTKWikiExamples stand-alone
-- VTKWikiExamples: Building VTKWikiExamples stand-alone - no
-- VTKWikiExamples: Setting executables prefix
-- VTKWikiExamples: Setting executables prefix - yes [prefix: wiki]
[...]
```

The test label is already set in ExampleTesting CMake module.

Implementing Bill's changes from the C++ version.

Adding the DisplacementPlot example.

Adding PlateVibration.

Fixing Spring.cxx, also adding classes used to Fig 6-12.

Replacing WritePNG with WriteImage.