python 3 migration

CONTRIBUTING.md

Utest/Validation/1test_1D/run_validation_1.py

Utest/Validation/2test_2D/run_validation_2.py

Utest/Validation/3test_UO/run_validation_3.py

Utest/Validation/6test_KO/run_validation_6.py

Utest/juelich_tests/test_1/runtest_juelich_1.py

Utest/juelich_tests/test_12/runtest_juelich_12.py

Utest/juelich_tests/test_14/runtest_juelich_14.py

Utest/juelich_tests/test_15/runtest_juelich_15.py

Utest/juelich_tests/test_2/runtest_juelich_2.py

Utest/juelich_tests/test_3/runtest_juelich_3.py

Utest/juelich_tests/test_4/runtest_juelich_4.py

Utest/juelich_tests/test_5/runtest_juelich_5.py

Utest/juelich_tests/test_6/runtest_juelich_6.py

Utest/juelich_tests/test_7.1/runtest_juelich_7_1.py

Utest/juelich_tests/test_7.2/runtest_juelich_7_2.py

Utest/juelich_tests/test_7/r_untest_juelich_7.py

Utest/juelich_tests/test_8/runtest_juelich_8.py

Utest/juelich_tests/test_9/runtest_juelich_9.py

Utest/makeini.py