ENH: Create project to build ITK module tests as an application
ENH: Create project to build ITK module tests as an application

Add an "ITKTestExternal" project that builds all ITK module test
directories as a single application outside of the main ITK build.  It
may build against an ITK build tree or an ITK install tree.  This will
ensure that ITK presents in its public interface everything that we
test, thus ensuring that everything is available to applications.

Change-Id: I2fb1e1e6112871c9adc221fc220e939505c68a2c

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