NO ITK_DATA_ROOT is only a problem if Testing ON
NO ITK_DATA_ROOT is only a problem if Testing ON

The absence of the ITK_DATA_ROOT CMake variable should only
report an error message if the CMake flag BUILD_TESTING is ON.
Otherwise, the absence of the Testing/Data is not a problem.

Change-Id: If2a64d84095a127792816b099fa92afa735d8d47

CapeDrew/DCMTK-ITK,hendradarwin/ITK,malaterre/ITK,itkvideo/ITK,cpatrick/ITK-RemoteIO,InsightSoftwareConsortium/ITK,Kitware/ITK,hjmjohnson/ITK,BlueBrain/ITK,stnava/ITK,thewtex/ITK,malaterre/ITK,LucHermitte/ITK,itkvideo/ITK,spinicist/ITK,stnava/ITK,heimdali/ITK,CapeDrew/DCMTK-ITK,rhgong/itk-with-dom,vfonov/ITK,stnava/ITK,richardbeare/ITK,LucHermitte/ITK,biotrump/ITK,jcfr/ITK,eile/ITK,spinicist/ITK,malaterre/ITK,BlueBrain/ITK,CapeDrew/DITK,eile/ITK,richardbeare/ITK,vfonov/ITK,LucasGandel/ITK,CapeDrew/DITK,CapeDrew/DITK,jmerkow/ITK,hendradarwin/ITK,ajjl/ITK,LucasGandel/ITK,CapeDrew/DITK,vfonov/ITK,zachary-williamson/ITK,daviddoria/itkHoughTransform,heimdali/ITK,hinerm/ITK,LucasGandel/ITK,malaterre/ITK,paulnovo/ITK,cpatrick/ITK-RemoteIO,fedral/ITK,atsnyder/ITK,itkvideo/ITK,BlueBrain/ITK,Kitware/ITK,GEHC-Surgery/ITK,jcfr/ITK,msmolens/ITK,atsnyder/ITK,LucasGandel/ITK,fedral/ITK,BRAINSia/ITK,hinerm/ITK,jcfr/ITK,daviddoria/itkHoughTransform,stnava/ITK,hjmjohnson/ITK,malaterre/ITK,malaterre/ITK,biotrump/ITK,hendradarwin/ITK,Kitware/ITK,zachary-williamson/ITK,PlutoniumHeart/ITK,jmerkow/ITK,daviddoria/itkHoughTransform,hjmjohnson/ITK,heimdali/ITK,atsnyder/ITK,rhgong/itk-with-dom,jcfr/ITK,hendradarwin/ITK,wkjeong/ITK,thewtex/ITK,zachary-williamson/ITK,paulnovo/ITK,GEHC-Surgery/ITK,fbudin69500/ITK,itkvideo/ITK,PlutoniumHeart/ITK,jcfr/ITK,fuentesdt/InsightToolkit-dev,daviddoria/itkHoughTransform,wkjeong/ITK,jcfr/ITK,BRAINSia/ITK,daviddoria/itkHoughTransform,zachary-williamson/ITK,msmolens/ITK,InsightSoftwareConsortium/ITK,ajjl/ITK,jcfr/ITK,BRAINSia/ITK,hjmjohnson/ITK,wkjeong/ITK,blowekamp/ITK,ajjl/ITK,CapeDrew/DCMTK-ITK,itkvideo/ITK,fbudin69500/ITK,cpatrick/ITK-RemoteIO,msmolens/ITK,biotrump/ITK,LucasGandel/ITK,fedral/ITK,zachary-williamson/ITK,itkvideo/ITK,heimdali/ITK,CapeDrew/DCMTK-ITK,vfonov/ITK,fbudin69500/ITK,InsightSoftwareConsortium/ITK,fbudin69500/ITK,rhgong/itk-with-dom,thewtex/ITK,zachary-williamson/ITK,spinicist/ITK,hendradarwin/ITK,BlueBrain/ITK,hinerm/ITK,wkjeong/ITK,fuentesdt/InsightToolkit-dev,stnava/ITK,BlueBrain/ITK,hjmjohnson/ITK,daviddoria/itkHoughTransform,LucHermitte/ITK,msmolens/ITK,jmerkow/ITK,itkvideo/ITK,msmolens/ITK,atsnyder/ITK,stnava/ITK,paulnovo/ITK,spinicist/ITK,PlutoniumHeart/ITK,LucHermitte/ITK,heimdali/ITK,GEHC-Surgery/ITK,CapeDrew/DITK,daviddoria/itkHoughTransform,jmerkow/ITK,heimdali/ITK,hendradarwin/ITK,eile/ITK,rhgong/itk-with-dom,LucasGandel/ITK,GEHC-Surgery/ITK,fbudin69500/ITK,ajjl/ITK,BRAINSia/ITK,LucasGandel/ITK,richardbeare/ITK,eile/ITK,fuentesdt/InsightToolkit-dev,wkjeong/ITK,cpatrick/ITK-RemoteIO,msmolens/ITK,thewtex/ITK,atsnyder/ITK,PlutoniumHeart/ITK,hinerm/ITK,blowekamp/ITK,fedral/ITK,fbudin69500/ITK,fuentesdt/InsightToolkit-dev,LucHermitte/ITK,hjmjohnson/ITK,CapeDrew/DITK,CapeDrew/DITK,biotrump/ITK,hjmjohnson/ITK,GEHC-Surgery/ITK,fuentesdt/InsightToolkit-dev,daviddoria/itkHoughTransform,stnava/ITK,atsnyder/ITK,itkvideo/ITK,heimdali/ITK,cpatrick/ITK-RemoteIO,itkvideo/ITK,PlutoniumHeart/ITK,BlueBrain/ITK,fuentesdt/InsightToolkit-dev,Kitware/ITK,paulnovo/ITK,zachary-williamson/ITK,spinicist/ITK,InsightSoftwareConsortium/ITK,GEHC-Surgery/ITK,LucHermitte/ITK,thewtex/ITK,rhgong/itk-with-dom,malaterre/ITK,cpatrick/ITK-RemoteIO,rhgong/itk-with-dom,fedral/ITK,CapeDrew/DITK,hinerm/ITK,blowekamp/ITK,Kitware/ITK,daviddoria/itkHoughTransform,ajjl/ITK,fuentesdt/InsightToolkit-dev,LucHermitte/ITK,InsightSoftwareConsortium/ITK,blowekamp/ITK,jcfr/ITK,eile/ITK,eile/ITK,vfonov/ITK,fedral/ITK,wkjeong/ITK,msmolens/ITK,BlueBrain/ITK,richardbeare/ITK,PlutoniumHeart/ITK,eile/ITK,fedral/ITK,BlueBrain/ITK,cpatrick/ITK-RemoteIO,hendradarwin/ITK,paulnovo/ITK,spinicist/ITK,eile/ITK,zachary-williamson/ITK,rhgong/itk-with-dom,stnava/ITK,fuentesdt/InsightToolkit-dev,ajjl/ITK,richardbeare/ITK,jmerkow/ITK,fuentesdt/InsightToolkit-dev,CapeDrew/DCMTK-ITK,fedral/ITK,atsnyder/ITK,Kitware/ITK,heimdali/ITK,CapeDrew/DCMTK-ITK,stnava/ITK,hinerm/ITK,msmolens/ITK,zachary-williamson/ITK,InsightSoftwareConsortium/ITK,malaterre/ITK,hinerm/ITK,GEHC-Surgery/ITK,BRAINSia/ITK,blowekamp/ITK,InsightSoftwareConsortium/ITK,BRAINSia/ITK,jmerkow/ITK,hendradarwin/ITK,CapeDrew/DCMTK-ITK,wkjeong/ITK,vfonov/ITK,paulnovo/ITK,PlutoniumHeart/ITK,vfonov/ITK,biotrump/ITK,biotrump/ITK,ajjl/ITK,eile/ITK,rhgong/itk-with-dom,CapeDrew/DCMTK-ITK,spinicist/ITK,biotrump/ITK,fbudin69500/ITK,jmerkow/ITK,ajjl/ITK,thewtex/ITK,paulnovo/ITK,spinicist/ITK,hinerm/ITK,fbudin69500/ITK,jmerkow/ITK,hinerm/ITK,wkjeong/ITK,cpatrick/ITK-RemoteIO,blowekamp/ITK,blowekamp/ITK,Kitware/ITK,LucasGandel/ITK,vfonov/ITK,atsnyder/ITK,PlutoniumHeart/ITK,BRAINSia/ITK,thewtex/ITK,richardbeare/ITK,biotrump/ITK,vfonov/ITK,blowekamp/ITK,GEHC-Surgery/ITK,CapeDrew/DITK,atsnyder/ITK,LucHermitte/ITK,spinicist/ITK,richardbeare/ITK,CapeDrew/DCMTK-ITK,paulnovo/ITK,malaterre/ITK