Localization support

Localization support. Finnish language added as a second language for the system. Also fixed an issue that could have shown direct error messages to the end users.

Needs testing before merge

tests/test_example.py

@@ -5,7 +5,3 @@ from conftests import client, app
 def test_config():
     assert not create_app().testing
     assert create_app({'TESTING': True}).testing
-
-def test_hello(client):
-    response = client.get('/hello') #, headers={'Accept-Language': 'en_US'}
-    assert response.data == b'Hello, World!'
\ No newline at end of file