Do not require QWidget in decorator generated by ctkWrapPythonQt

Including QObject is sufficient, this was an oversight of the initial
implementation added in d3f81f4 (Move all PythonQt wrapping code into
one script. See #449)

Inspired-by: Eric Heim <e.heim@dkfz-heidelberg.de>

CMake/ctkWrapPythonQt.py

@@ -168,7 +168,7 @@ def ctk_wrap_pythonqt(target, namespace, output_dir, input_files, extra_verbose)
 #ifndef __${namespace}_${target}_h
 #define __${namespace}_${target}_h
 
-#include <QWidget>
+#include <QObject>
 ${includes}
 ${pythonqtWrappers}
 #endif