ENH: Use ITK FilterWatcher and rename DifferenceImageFilter2

"itktubeFilterWatcher" is identical to <itkFilterWatcher.h> so use the ITK
version. itkDifferenceImageFilter2 used to clash with itkDifferenceImageFilter,
but now does not with new naming convention and namespace, so rename.

Change-Id: I17743b3f0f34bf000cbace078afc1b62b61c2d8d
ENH: Use itkMacro.h instead of tubeMacro.h

tubeMacro.h is very rarely used and itkMacro.h contains at least the same
functionality, so always use itkMacro.h.

Change-Id: Ic8a0293aaffc605cc4b9c94a90d6b5b4ea995fdf
Merge topic 'UseITKFilterWatcher'

4092ac6 ENH: Use ITK FilterWatcher and rename DifferenceImageFilter2
Merge topic 'UseITKMacro'

038812d ENH: Use itkMacro.h instead of tubeMacro.h