Fix serial warnings

rwx/src/main/java/org/commonjava/rwx/error/XmlRpcException.java

@@ -23,6 +23,7 @@ public class XmlRpcException
 {
     private static final long serialVersionUID = 1L;
 
+    @SuppressWarnings( "serial" )
     private Object[] params;
 
     private transient String formatted;

rwx/src/main/java/org/commonjava/rwx/error/XmlRpcFaultException.java

@@ -23,6 +23,7 @@
 public class XmlRpcFaultException
                 extends XmlRpcException
 {
+    private static final long serialVersionUID = 1L;
 
     private Fault fault;
 

rwx/src/main/java/org/commonjava/rwx/model/Fault.java

@@ -15,6 +15,8 @@
  */
 package org.commonjava.rwx.model;
 
+import java.io.Serializable;
+
 /**
  * XML-RPC faults are a type of responses.
  * If there was a problem in processing an XML-RPC request, the methodResponse
@@ -23,8 +25,11 @@
  * <p>
  * Created by ruhan on 7/13/17.
  */
-public final class Fault extends RpcObject
+public final class Fault extends RpcObject implements Serializable
 {
+    private static final long serialVersionUID = 1L;
+
+    @SuppressWarnings( "serial" )
     private Object value;
 
     public Object getValue()

rwx/src/main/java/org/commonjava/rwx/vocab/Nil.java

@@ -58,6 +58,8 @@ private Object writeReplace()
     private static class Proxy
         implements Externalizable
     {
+        private static final long serialVersionUID = 1L;
+
         public Proxy()
         {