Add missing license headers and Serializable implementations.

src/com/vaadin/terminal/gwt/client/communication/ClientToServerRpc.java

+/*
+@VaadinApache2LicenseForJavaFiles@
+ */
+
 package com.vaadin.terminal.gwt.client.communication;
 
 import com.vaadin.terminal.gwt.client.ApplicationConnection;

src/com/vaadin/terminal/gwt/client/communication/JsonEncoder.java

+/*
+@VaadinApache2LicenseForJavaFiles@
+ */
+
 package com.vaadin.terminal.gwt.client.communication;
 
 import java.util.Map;

src/com/vaadin/terminal/gwt/client/communication/MethodInvocation.java

+/*
+@VaadinApache2LicenseForJavaFiles@
+ */
+
 package com.vaadin.terminal.gwt.client.communication;
 
 /**

src/com/vaadin/terminal/gwt/server/JsonDecoder.java

+/*
+@VaadinApache2LicenseForJavaFiles@
+ */
+
 package com.vaadin.terminal.gwt.server;
 
+import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.Iterator;
  * 
  * @since 7.0
  */
-public class JsonDecoder {
+public class JsonDecoder implements Serializable {
 
     /**
      * Convert a JSON array with two elements (type and value) into a

src/com/vaadin/terminal/gwt/server/PaintableIdMapper.java

+/*
+@VaadinApache2LicenseForJavaFiles@
+ */
+
 package com.vaadin.terminal.gwt.server;
 
+import java.io.Serializable;
+
 import com.vaadin.terminal.Paintable;
 
 /**
  * 
  * @since 7.0
  */
-public interface PaintableIdMapper {
+public interface PaintableIdMapper extends Serializable {
     /**
      * Get the {@link Paintable} instance corresponding to a paintable id.
      * 

src/com/vaadin/terminal/gwt/server/RpcManager.java

+/*
+@VaadinApache2LicenseForJavaFiles@
+ */
+
 package com.vaadin.terminal.gwt.server;
 
+import java.io.Serializable;
+
 import com.vaadin.terminal.gwt.client.communication.MethodInvocation;
 
 /**
  * 
  * @since 7.0
  */
-public interface RpcManager {
+public interface RpcManager extends Serializable {
     public void applyInvocation(MethodInvocation invocation);
 }

src/com/vaadin/terminal/gwt/server/RpcTarget.java

+/*
+@VaadinApache2LicenseForJavaFiles@
+ */
+
 package com.vaadin.terminal.gwt.server;
 
+import java.io.Serializable;
+
 import com.vaadin.terminal.VariableOwner;
 
 /**
  * 
  * @since 7.0
  */
-public interface RpcTarget {
+public interface RpcTarget extends Serializable {
     /**
      * Returns the RPC manager instance to use when receiving calls for an RPC
      * interface.

src/com/vaadin/terminal/gwt/server/ServerRpcManager.java

+/*
+@VaadinApache2LicenseForJavaFiles@
+ */
+
 package com.vaadin.terminal.gwt.server;
 
 import java.lang.reflect.Field;

src/com/vaadin/terminal/gwt/widgetsetutils/RpcProxyGenerator.java

+/*
+@VaadinApache2LicenseForJavaFiles@
+ */
+
 package com.vaadin.terminal.gwt.widgetsetutils;
 
 import java.io.PrintWriter;