ENH: Support VTK6.

1) 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

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) Remove Pipeline Update Methods from vtkDataObject.
http://www.vtk.org/Wiki/VTK/VTK_6_Migration/Removal_of_Update.
ENH: Merge VTK6 support by @finetjul.
Merge remote-tracking branch 'remotes/roots/master'

Conflicts:
	MRML/vtkIGTLToMRMLImage.cxx