COMP: Pass CMAKE_BUILD_TYPE to all projects

Thanks to Hans Johnson <hans-johnson@uiowa.edu> for reporting the issue.

See #418
Allow FindDCMTK.cmake to be re-used directly adding missing module.

Usage of 'find_package_handle_standard_args' was initially introduced
by commit 52d9539f5e7.

For more details about the issue, see http://forum.dcmtk.org/viewtopic.php?f=1&t=3906&p=15599#p15599

See #431
ENH: Support VTK6 in CTK

1) Support vtk6 to build system.
http://www.vtk.org/Wiki/VTK/Build_System_Migration
Give users a build option between vtk5 and vtk6.
Solve vtk library python wrapping for VTK 6

2) Replace SetInput() with SetInputData() and SetInputConnection(), the same kind of functions include SetInput1(), SetInput2(), AddInput() and SetSource().
http://www.vtk.org/Wiki/VTK/VTK_6_Migration/Replacement_of_SetInput

3) Change scalars manipulation functions
http://www.vtk.org/Wiki/VTK/VTK_6_Migration/Changes_to_Scalars_Manipulation_Functions.
http://vtk.org/Wiki/VTK/VTK6/Migration/WikiExamples#Improve.

4) VTK requires #include <vtkVersion.h> to use the VTK_xxx_VERSION preprocessor directives.
http://vtk.org/Wiki/VTK/VTK6/Migration/WikiExamples#Improve

5) Remove deprecated Macro.
The following two macros were deprecated in VTK 5.0 that were still supported, but have now been eliminated:
vtkTypeRevisionMacro has been replaced with vtkTypeMacro; vtkCxxRevisionMacro has been removed.
http://www.visitusers.org/index.php?title=VTK_6.0_Upgrade

6)Refactor functions in vtkMRMLVolumeNode and its subclasses.
Use ImageDataPort instead of ImageData