update test_main_app in test_sams_hub.py to fix issue #12

the test now uses copy of main_app string in hub.config. This is
important to ensure the hub_class addApp method compares the string
value (not it's identity) of app.name to determine it is the main app.

test/test_sams_hub.py

@@ -53,7 +53,7 @@ class CaseSAMSHubWithMainApp(unittest.TestCase):
       with self.subTest(main_app = main_app, extra_app = extra_app):
         hub = SAMSHub(
           name = 'test',
-          config = {'default_language': 'de', 'main_app' : main_app}
+          config = {'default_language': 'de', 'main_app' : ''.join(main_app)}
         )
         expected_names = [
           'Hauptanwendung Punkt 1', 'Hauptanwendung Punkt 2',