Cleanup vtkCaveSynchronizedRenderers

The vtkCaveSynchronizedRenderers class has been cleaned up.

In that context ComputeCamera has been deprecated in favor of InitializeCamera and the following protected members are now private.

• double EyeSeparation;
• int NumberOfDisplays;
• double** Displays;
• double DisplayOrigin[3];
• double DisplayX[3];
• double DisplayY[3];
• int once;