Add a side-effect property to Interface Operation

• se attribute on operation
• optional information

<operation name="GetStockQuote"
           pattern="http://www.w3.org/2003/11/wsdl/in-out"
           se="http://www.w3.org/2004/02/wsdl/se/safe">
  <input message="tns:gsqReq"/>
  <output message="tns:gsqResp"/>
</operation>