title: PrimeFaces datatable initial sortBy does not work
body: <p>I have a PrimeFaces 3.2 DataTable using apache myfaces 2.0.2 . I want a initial sort. My JSF looks like:</p>
  
  <pre><code>&lt;p:dataTable  id="serverdata" var="serverdata" sortBy="#{serverdata[0]}" sortOrder="descending" 
                  value="#{ serverDataTable.list }" rows="10" editable="true" 
                  paginator="true" rowsPerPageTemplate="10,20,50"
                  paginatorTemplate="{CurrentPageReport}  {FirstPageLink} {PreviousPageLink} {PageLinks} {NextPageLink} {LastPageLink} {RowsPerPageDropdown}"&gt;
                  &lt;f:facet name="header"&gt;  
                     Datatable
                   &lt;/f:facet&gt;
                  &lt;p:column&gt;
                      &lt;f:facet name="header"&gt;
                          &lt;h:outputText value="Datum"/&gt;
                      &lt;/f:facet&gt;
                      &lt;h:outputText value="#{serverdata[0]}"&gt;
                      &lt;/h:outputText&gt;
                  &lt;/p:column&gt;
  </code></pre>
  
  <p>But I get a <code>UnsupportedOperationException: The result list is read-only.</code> When I delete the sortBy tag in  it works fine.</p>
  
  <p>So my question:
  How can I realize an initial sort?</p>