insightoolkit: cmake viral dep and gdcm

[Mathieu Malaterre <mathieu.malaterre@gmail.com>]

Hi Steve,

  While trying to build GoFigure2, I found out that cmake viral
dependencies is striking again (*). I see that you fixed 580816, I am
wondering if I should re-open this bug or would you rather a new one.

  The point is that a project that cmake include itk should not
require gdcm (unless of course it is actually using it).

Thanks

(*)
-- GoFigure2 version 0.4.2
CMake Warning at /usr/lib/InsightToolkit/UseITK.cmake:103 (FIND_PACKAGE):
  Could not find module FindGDCM.cmake or a configuration file for package
  GDCM.

  Adjust CMAKE_MODULE_PATH to find FindGDCM.cmake or set GDCM_DIR to the
  directory containing a CMake configuration file for GDCM.  The file will
  have one of the following names:

    GDCMConfig.cmake
    gdcm-config.cmake

Call Stack (most recent call first):
  CMakeLists.txt:164 (INCLUDE)


CMake Error at /usr/lib/InsightToolkit/UseITK.cmake:107 (MESSAGE):
  UseITK could not load GDCM settings from "GDCM_DIR-NOTFOUND" even through
  ITK was built using GDCM from this location.
Call Stack (most recent call first):
  CMakeLists.txt:164 (INCLUDE)


-- Configuring incomplete, errors occurred!
dh_auto_configure: cmake .. -DCMAKE_INSTALL_PREFIX=/usr
-DCMAKE_VERBOSE_MAKEFILE=ON returned exit code 1