ENH: Increase itk::HeldIsotropicWavelet coverage.
ENH: Increase itk::HeldIsotropicWavelet coverage.

Test the polynomial order exception when exceeding the maximum value of
6.

Exercise basic object methods.

phcerdan/ITKIsotropicWavelets,jhlegarreta/ITKIsotropicWavelets,phcerdan/ITKIsotropicWavelets,jhlegarreta/ITKIsotropicWavelets