Remove the ImageAnalysis library from AIRS.

The vtkImageRangeCalculator has been superseded by the
vtkImageHistogramStatistics class, and vtkSimpleShapeStencilSource
by the vtkROIStencilSource class.
Remove vtkCenteredTransform, vtkImageFastBlur.

The vtkCenteredTransform was never used, and vtkImageFastBlur
has been superseded by the capabilities of vtkImageResize.
Move all the AtamaiWarp-related classes.
Remove the MNIXFM IO classes, they're in VTK now.
Update ImageRegistration classes for VTK 6 compatibility.
Remove vtkImageFloodFill, use vtkImageThresholdConnectivity.
Convert ImageSegmentation classes to VTK 6.
Add the VTK 6 libs to LINK_LIBRARIES.
Update the "register" program for VTK 6.
Update the examples for VTK 6.
Fix an "if" that should have been "ifdef".
The VTK_ID_MAX macro isn't defined in VTK 5.
Fix register.cxx so it actually works with VTK 6.
Force updating of WholeExtent on VTK 5.

There was some difficulty because VTK tends to make the UpdateExtent
sticky, so that it remains the same on subsequent updates if not
explicity set to a new value.  Unfortunately, if the WholeExtent had
shrunk, then the UpdateExtent would be larger than the WholeExtent
and hence would cause a error.