Illustrate use of ServiceReference for Web services and Web hosting services

We should provide some more examples of the use of ServiceReferences for typical Web and Web service-related scenarios. 
This will help readers understand better section 4.2.3 and how to fill it.

In the case of referring to Web services, we can point using syntax of the WS-PolicyReference and WS-Addressing 
specification:

        <wsag:ServiceReference wsag:Name="TradeServiceRef" wsag:ServiceName="Trade">
	    <wsp:AppliesTo> 
             <wsa:EndpointReference>
	          <wsa:Address>/myService/trade/</wsa:Address>
                <wsa:PortType>trade:TradePortType</wsa:PortType>
                <wsa:Service>trade:TradeService</wsa:Service> 
	       </wsa:EndpointReference>
	    </wsp:AppliesTo>
        </wsag:ServiceReference>

Web pages scopes can be defined using a corresponding XPointer expression. Each page matching this expression is subject
 to the guarantees referring to this service.

        <wsag:ServiceReference wsag:Name="TradeServiceRef" wsag:ServiceName="TradeWebApp">
             http://fabrikam.net/xpointer(/trade/*)
        </wsag:ServiceReference>