MovingImagePyramidBase, FixedImagePyramidBase have different defaults for "NumberOfResolutions"

[N-Dekker]

MovingImagePyramidBase::SetMovingSchedule() uses zero as default value for "NumberOfResolutions", and then produces an error message when it is indeed zero! Looking at commit ab62f3d (September 6, 2004)

elastix/src/Core/ComponentBaseClasses/elxMovingImagePyramidBase.hxx

Lines 38 to 43 in ab62f3d

	unsigned int numberOfResolutions = 0;
	m_Configuration->ReadParameter( numberOfResolutions, "NumberOfResolutions", 0, true );
	if ( numberOfResolutions == 0 )
	{
	xl::xout["error"] << "ERROR: NumberOfResolutions not specified!" << std::endl;
	}

On the other hand, commit f84ac0d (ENH: First checkin of a generic pyramid..., Feb 2, 2012) has changed the default for "NumberOfResolutions" in FixedImagePyramidBase to 3, and silently accepts zero as well, assuming it should be one:

elastix/src/Core/ComponentBaseClasses/elxFixedImagePyramidBase.hxx

Lines 104 to 107 in f84ac0d

	unsigned int numberOfResolutions = 3;
	this->m_Configuration->ReadParameter( numberOfResolutions,
	"NumberOfResolutions", 0, true );
	if ( numberOfResolutions == 0 ) numberOfResolutions = 1;

Other places (MultiMetricMultiResolutionRegistration, MultiResolutionRegistration) also use 3 as default value.

Should MovingImagePyramidBase::SetMovingSchedule() also use 3 as default value?

[mstaring]

let's use 3 everywhere as a default