bug: contiguous itemsets are treated as nested when itemset is refreshed

> Lets say I have a <xf:select1> with multiple adjacent itemsets, eg
>
>     <xf:select1>
>         <xf:itemset bind="bind-types">
>             <xf:label ref="@value"/>
>             <xf:value ref="@value"/>
>         </xf:itemset>
>         <xf:itemset bind="bind-types2">
>             <xf:label ref="@value"/>
>             <xf:value ref="@value"/>
>         </xf:itemset>
>     </xf:select1>
>
> The intial HTML is correctly generated with a single combined set of
> options from each itemset. If however the itemsets change and the option
> are rebuilt, the second itemset is incorrectly being treated as a nested
> itemset, and generated as a sub-option group of the first. Also the last
> option of the first itemset isn't available as an option, instead just
> as the label as the nested option group.
>
> Attached is an example showing the problem: initially the options are
> correct. If you uncheck then recheck the boolean flag, the rebuilt
> dropdown is incorrect.
>
> It looks like
> org.orbeon.oxf.xforms.control.controls.XFormsSelect1Control is not
> decrementing hierarchyLevel in the endElement() method (for both choices
> & itemsets). Intially I thought that a simple implementation of
>
>             public void endElement(Element element) {
>                
>                  if ("itemset".equals(element.getName()) ||
> "choices".equals(element.getName())) {
>                      hierarchyLevel--;
>                  }
>             }
>
> might work, but this is too simplistic because  hierarchyLevel is not
> always incremented in startElement, and it's not clear that it's always
> incremented by just one.
>
> It's a pity the (correct) logic in XFormsSelect1Handler which does the
> initial generatation isn't being shared here, to reduce the duplication
> of some fairly tricky code.
>
> Adrian
>