enable SOAP XML logging when invoke web service

Hi,

I need to see what actually is send and received when something is failing, I review the code and see like that is no logging for this.

the code is pretty simple to implements:

make a decorator Writer:

```
private class EchoWriter extends Writer
{
Writer out;

StringBuilder buf = new StringBuilder();

public EchoWriter(Writer out)
{
this.out = out;
}

public void write(String b) throws IOException
{
buf.append(b);
out.write(b);
}

public void write(int b) throws IOException
{
buf.append((char)b);
out.write(b);
}

public void write(char[] b) throws IOException
{
//System.out.print(b);
out.write(b);
}

public void write(String b, int offset, int len) throws IOException
{
//System.out.print(b);
out.write(b, offset, len);
}

public void write(char[] b, int offset, int len) throws IOException
{
//System.out.print(b);
out.write(b, offset, len);
}

public void close() throws IOException
{
out.close();
}

public void flush() throws IOException
{
System.out.println(buf.toString()); //logging start here
System.out.println("-----------------");
buf = new StringBuilder();

out.flush();
}
}
```

add it to

MXSerializer.java

out = new EchoWriter(new OutputStreamWriter(os));

and that it !