COMP: Fix python print import for .pth file creation

Fixes the following error:
CMake Error at Wrapping/install_wrapitk_compatibility.cmake:3 (file):
  file called with unknown argument
  "/tmp/imichka-insighttoolkit-QtOS/itk-build/Wrapping/Generators/Python/det_spp.py",
  line 2 from __future__ import print_functionSyntaxError: from __future__
  imports must occur at the beginning of the file"".

Change-Id: I7163eb556074c4e8d403254ce7e83986e959c7b6
COMP: Fix print import statement in itkExtras.py

Will fix the following error in the tests:

Traceback (most recent call last):
  File "/home/kevin/kitware/ITK/Wrapping/Generators/Python/Tests/CurvatureFlowImageFilter.py", line 24, in <module>
    import itk
  File "/home/kevin/kitware/ITK_Build/Wrapping/Generators/Python/itk.py", line 24, in <module>
    import itkExtras
  File "/home/kevin/kitware/ITK_Build/Wrapping/Generators/Python/itkExtras.py", line 28
    from __future__ import print_function
SyntaxError: from __future__ imports must occur at the beginning of the file
itkTestDriver: Process exited with return value: 1

Change-Id: I3880862f1fd85f05dd9e85d347bd5e33498275ec
Merge topic 'FixPrintImport'

ccc97cc3 COMP: Fix python print import for .pth file creation
Merge topic 'FixPythonTestPrintImports'

69f406fb COMP: Fix print import statement in itkExtras.py