Add online (aka ReplayCenter) module

Add localization extra (formally known as LocalizedResourcePack)
Add version checker extra

src/main/java/com/replaymod/online/Setting.java

@@ -0,0 +1,15 @@
+package com.replaymod.online;
+
+import com.replaymod.core.SettingsRegistry;
+
+public final class Setting<T> extends SettingsRegistry.SettingKeys<T> {
+    public static final Setting<Boolean> SKIP_LOGIN_PROMPT = make("skipLoginPrompt", null, false);
+
+    private static <T> Setting<T> make(String key, String displayName, T defaultValue) {
+        return new Setting<>(key, displayName, defaultValue);
+    }
+
+    public Setting(String key, String displayString, T defaultValue) {
+        super("online", key, displayString == null ? null : "replaymod.gui.settings." + displayString, defaultValue);
+    }
+}