BUG: Fix ResampleImage XML

The output volume had a string type where it really should be an image to
be correctly integrated with slicer's GUI.
The optionnal image didn't have any channel which prevented it from
working.

Change-Id: I3cca295456dd16d268185e5004cf4ad6a1937f69
Merge topic 'FixResampleXML'

af3fc0a BUG: Fix ResampleImage XML
ENH: Add new tubeMacro.h and very lightweight Object base class

My original thought was that everything could be in itk::tube and use
itkMacro.h. That idea was abandoned, so here is a cut down and
simplified version of itkMacro.h / vtkSetGet.h with helper macros for classes
that are not derived from ITK or VTK.

The Object base class simplifies printing out non-ITK or -VTK derived classes
for debugging. No smart pointers or anything heavyweight.

Change-Id: Ib710d42414b226bae3141fc53e084dcb6ac15511