ENH: If the option --concatenateOnly is selected, the input image can be a scalar image if a reference image is given. In that case, if no reference image is given, an error will occur.
Merge branch 'concatenateOnly'

Conflicts:
	Source/ResampleDTI.cxx
	Source/itkDiffusionTensor3DRead.h
	Source/itkDiffusionTensor3DRead.txx
ENH: If the option --concatenateOnly is selected, the input image can be a scalar image if a reference image is given. In that case, if no reference image is given, an error will occur.