ENH: Allow tests not in any module with label 'ITKModular'
ENH: Allow tests not in any module with label 'ITKModular'

Teach the add_test() override macro to allow tests to be added outside
of modules.  Use the main project label for such tests.  While at it,
remove the unused ${itk-module}_TESTS property and ensure the
'itk-module' variable is not set outside of modules.

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