Task SW-516: Change all hashbangs from pointing to python2 or default python to python3

bin/feedback2sip

-#!/usr/bin/python
+#!/usr/bin/env python3
 
 from lofar.lta.sip.feedback import main
 import sys

bin/validatesip

-#!/usr/bin/python
+#!/usr/bin/env python3
 
 from lofar.lta.sip.validator import main
 import sys

bin/visualizesip

-#!/usr/bin/python
+#!/usr/bin/env python3
 
 from lofar.lta.sip.visualizer import main
 import sys

lib/constants_generator.py

-#!/usr/bin/python
+#!/usr/bin/env python3
 
 # This module can be used to auto-generate a list of constant definitions based on value restrictions (defined as
 # enumerations in the XSD). These are dynamically retrieved from the pyxb-generated API module and in most cases can

lib/feedback.py

-#!/usr/bin/python
+#!/usr/bin/env python3
 
 import sys
 import pprint

lib/siplib.py

-#!/usr/bin/python
+#!/usr/bin/env python3
 
 # This module provides functions for easy creation of a Lofar LTA SIP document.
 # It builds upon a Pyxb-generated API from the schema definition, which is very clever but hard to use, since

lib/visualizer.py

-#!/usr/bin/python
+#!/usr/bin/env python3
 
 from graphviz import Digraph
 import sys

test/test_feedback.py

-#!/usr/bin/python
+#!/usr/bin/env python3
 
 # Copyright (C) 2012-2015    ASTRON (Netherlands Institute for Radio Astronomy)
 # P.O. Box 2, 7990 AA Dwingeloo, The Netherlands

test/test_siplib.py

-#!/usr/bin/python
+#!/usr/bin/env python3
 
 # Copyright (C) 2012-2015    ASTRON (Netherlands Institute for Radio Astronomy)
 # P.O. Box 2, 7990 AA Dwingeloo, The Netherlands

test/test_validator.py

-#!/usr/bin/python
+#!/usr/bin/env python3
 
 # Copyright (C) 2012-2015    ASTRON (Netherlands Institute for Radio Astronomy)
 # P.O. Box 2, 7990 AA Dwingeloo, The Netherlands

test/test_visualizer.py

-#!/usr/bin/python
+#!/usr/bin/env python3
 
 # Copyright (C) 2012-2015    ASTRON (Netherlands Institute for Radio Astronomy)
 # P.O. Box 2, 7990 AA Dwingeloo, The Netherlands