Add online (aka ReplayCenter) module

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

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

@@ -0,0 +1,39 @@
+package com.replaymod.online;
+
+import net.minecraft.client.Minecraft;
+
+import java.util.Random;
+
+public class AuthenticationHash {
+
+    private static final Random random = new Random();
+
+    public AuthenticationHash() {
+        username = Minecraft.getMinecraft().getSession().getUsername();
+        currentTime = System.currentTimeMillis();
+        randomLong = random.nextLong();
+        hash = getAuthenticationHash();
+    }
+
+    public final String username;
+    public final long currentTime;
+    public final long randomLong;
+    public final String hash;
+
+    private String getAuthenticationHash() {
+        String md5 = username + currentTime + randomLong;
+
+        try {
+            java.security.MessageDigest md = java.security.MessageDigest.getInstance("MD5");
+            byte[] array = md.digest(md5.getBytes());
+            StringBuilder sb = new StringBuilder();
+            for (byte b : array) {
+                sb.append(Integer.toHexString((b & 0xFF) | 0x100).substring(1, 3));
+            }
+            return sb.toString();
+        } catch (java.security.NoSuchAlgorithmException e) {
+            e.printStackTrace();
+        }
+        return null;
+    }
+}