Removed __traits_version__ from json files

Created by: jjenthought

The workflow is a dictionary which contains lists of dictionaries, so only the traits_version keys in the top level dict were being removed. This changed the function so it should do it recursively. It seems fine but the only test is a on a single hardcoded example at the minute. Refs. issue https://github.com/force-h2020/force-bdss/issues/134

Fixes #134 (closed)

force_bdss/io/tests/test_workflow_writer.py

@@ -101,5 +101,5 @@ class TestWorkflowWriter(unittest.TestCase):
                              'K2': ['V1', 'V2', {'K1': 'V1', 'K2': 'V2', }],
                              'K4': ('V1', {},)}
 
-        test_result_dictionary = pop_recursive(test_dictionary, )
+        test_result_dictionary = pop_recursive(test_dictionary, 'K3')
         self.assertEqual(test_result_dictionary, result_dictionary)