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

 from tjts5901 import create_app
-from tjts5901.conftests import client, app
+from conftests import client, app
 
 
 def test_config():