Migrate everything on Gradle

Also added tasks to run the server & client separately

ChatApp/app/src/main/java/ChatAppClient.java

@@ -0,0 +1,15 @@
+import client.ClientConsole;
+
+import java.net.InetSocketAddress;
+
+public class ChatAppClient {
+    public static void main(String[] args) {
+        ClientConsole console = new ClientConsole(new InetSocketAddress("localhost", 6665));
+        try {
+            console.joinThread();
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+        System.out.println("End !");
+    }
+}