[RTC] Support mixed nested properties and complex elements

In OpenEJB we would like to be able to support arbitrary mixing of text based properties and complex elements. This patch adds support for this by merging all text sub nodes and attempting to read them in using java.util.Properties. This patch contains a test case which read the following xbean-spring element:

 
  <p:PizzaService id="pizzaService">
      cheese    Edam

    <!-- properties can have complex elements mixed in -->
    <p:topping>Salami</p:topping>

       size      17
  </p:PizzaService>