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

src/tjts5901/app.py

@@ -89,7 +89,7 @@ app = create_app()
 # a simple page that says hello
 @app.route("/hello")
 def hello():
-    return _('Hello, World!')
+    return (_('Hello, World!'))
 
 
 @app.route("/server-info")