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/translations/fi_FI/LC_MESSAGES/messages.po

@@ -378,7 +378,7 @@ msgstr "Huutokaupat"
 msgid "Delete"
 msgstr "Poista"
 
-#: tests/test_i18n.py:79 tests/test_i18n.py:103
+#: tests/test_i18n.py:58 tests/test_i18n.py:82
 msgid "Hello, World!"
 msgstr "Hei, Maailma"