Windup-296: Nested iteration queries automatically queries the payload 

https://issues.jboss.org/browse/WINDUP-296

In other words, this now works:
```
.addRule()
        .when(XmlFile.matchesXpath("/spring")  )
        .perform(
            Iteration.over()
            .when(XmlFile.matchesXpath("//bean"))
            .perform(/* XML that matches '/spring' and '//bean' also */ )
            .endIteration()
         )         
```