ENH: Support of VectorImage as template parameters for WarpImageFilter

[jmichel-otb]

This patch relates to issue #2895 ( https://issues.itk.org/jira/browse/ITK-2895#comment-27056 )

It is a straigthforward port of OTB patch provided by Julien Malik on his github page (see first comment)

Patch summary:

• In itkWarpImageFilter.h:
  • Replace HasNumericTraits concept checking on TInputImage::PixelType by checking on TInputImage::InternalPixelType, since HasNumericTraits will fail with VariableLengthVector as PixelType
• In itkWarpImageFilter.txx:
  • Changed instanciation of m_EdgePaddingValue member to avoid calling NumericTraits< PixelType >::Zero, which does not exist for VariableLengthVector
  • Add further initialization of m_EdgePaddingValue in BeforeThreadedGenerateData, so that it will generate a VariableLenghtVector of appropriate length if needed
  • Avoid calling DisplacementType::Dimension and use the GetLength method from NumericTraits instead, which will support both static and dynamic (VariableLengthVector) length
• In itkWarpImageFilterTest.cxx:
  • Added a simple test for template instanciation of WarpImageFilter using VectorImage for all three template parameters

Change-Id: I44fb183dd6a684a23312446b2bc2d62e7f8eff7b

[jmichel-otb]

Note that I initially planned to push this patch to gerrit, but I am behind a firewall and did not manage to get http push working, though I carefully followed http://www.itk.org/Wiki/ITK/Git/Account#Gerrit :
Fetching gerrit master
Pushing to gerrit
Password for 'http://jmichel-otb@review.source.kitware.com':
remote: Unauthorized
fatal: Authentication failed for 'http://jmichel-otb@review.source.kitware.com/p/ITK/'

I am quite sure this worked for me in the past (I have 3 merged patches and 1 abandonned logged in gerrit already).

[thewtex]

Uploaded to Gerrit here:

http://review.source.kitware.com/#/c/20310/