feat: Add Localization Manager

Created by: whitebear60

To add a new language to the app you need:

1. Create resources/de/griefed/resources/lang/lang_language code.lang file.
2. Add language code to the SUPPORTED_LANGUAGES list in Reference
3. Translate the app!

Please keep in mind that auto fallback to English when locale key doesn't exist in current language is not implemented yet. Now @Griefed need to replace all messages that he wants to be translatable with LocalizationManager.getLocalizedString(<translation key>) and, obviously, add this messages to lang_en_us.lang under translation keys that are exact the same as it mentioned in code.

src/main/java/de/griefed/ServerPackCreator/i18n/IncorrectLanguageException.java

+package de.griefed.ServerPackCreator.i18n;
+
+public class IncorrectLanguageException extends Exception {
+    public IncorrectLanguageException() {
+        super("Incorrect language specified");
+    }
+
+    public IncorrectLanguageException(String message) {
+        super(message);
+    }
+
+    public IncorrectLanguageException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public IncorrectLanguageException(Throwable cause) {
+        super(cause);
+    }
+}