Update PythonManager to use recent PythonQt version

The "patched-3" branch is rebased against r244 of PythonQt, it integrates
all backported changes specific to "patched-2" and also
include improvements by the upstream team. For a detailed list,
see https://github.com/commontk/PythonQt/compare/e2dce4...0a2486
Fix unused variable warnings in ctkAbstractPythonManager
Merge branch 'update-pythonqt-to-patched3-branch'

* update-pythonqt-to-patched3-branch:
  Fix unused variable warnings in ctkAbstractPythonManager
  Update PythonManager to use recent PythonQt version