STYLE: ITK_EXPORT had no use

The defintion of ITK_EXPORT was empty in all cases

This has been identified since 2003 as not being necessary
for builds. see https://issues.itk.org/jira/browse/ITK-3110

On Windows builds that need exports, they must
be unique per library, and that is not controlled by CMake now.

The PrintSelfCheck.tcl was the only remenant need for
This patch, and that is no longer being used, so that
file as been removed.

The ITK_EXPORT define was set to nothing and had no
known remaining purpose.  It was removed to make the
over all code easier to understand.  There was,
understandably, a bit of confusion about the
need for this being pervasive in the code.

It is currently backwards compatible to have
this in code, but at some future point it will
be removed.

From: Hans Johnson <hans-johnson@uiowa.edu>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22132 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: Adding option for SimpleITK as a shared library

SimpleITK has large internal libraries, which take an extremely long
time to link on windows when they are static. Creating shared
SimpleITK internal libraries can reduce linking time. Also the size
of the debug libraries are monstrous. Using shared libraries for
debug, reduce disc requirements, and can improve linking
times. However, these shared libraries take longer to load than the
monolithic target from static libraries.

This commits updates the build system:
1) Propagate SimpleITK_DIR into Slicer config.
2) Add SimpleITK lib path to runtime library path for build.
3) Add SimpleITK to be installed as a cmake project.
4) Add CMake variable Slicer_USE_SimpleITK_SHARED to turn on SimpleITK
as a shared library.

Co-authored-by: Jean-Christophe Fillion-Robin <jchris.fillionr@kitware.com>

From: Bradley Lowekamp <blowekamp@mail.nih.gov>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22133 3bd1e089-480b-0410-8dfb-8563597acbee