title: selectOneMenu filter by various columns and not just the label
body: <p>Looking at the "Advanced" example here: <a href="http://www.primefaces.org/showcase/ui/input/oneMenu.xhtml" rel="nofollow">http://www.primefaces.org/showcase/ui/input/oneMenu.xhtml</a>, I was able to have two columns in each of the options in my <code>oneMenu</code>, but the filtering only happens on the item's label. </p>
  
  <p>What I would like to be able to do is filter by either of the columns (unlike the example, both my columns contain only text, so they are filterable). Is this customization possible?</p>
  
  <p>Adding <code>filter="true"</code> to either of the <code>&lt;p:column&gt;</code>s doesn't seem to have any effect while the utility: <code>filterFunction</code> to write custom filtering rules seems to operate only on the label also!</p>
  
  <pre><code>&lt;p:outputLabel for="advanced" value="Advanced:"  /&gt;
  &lt;p:selectOneMenu id="advanced" value="#{selectOneMenuView.theme}" converter="themeConverter" panelStyle="width:180px"
                           effect="fade" var="t" style="width:160px" filter="true" filterMatchMode="startsWith"&gt;
    &lt;f:selectItems value="#{selectOneMenuView.themes}" var="theme" itemLabel="#{theme.displayName}" itemValue="#{theme}" /&gt;
    &lt;p:column style="width:10%"&gt;
      &lt;h:outputText styleClass="ui-theme ui-theme-#{t.name}" /&gt;
    &lt;/p:column&gt;
    &lt;p:column&gt;
      &lt;h:outputText value="#{t.displayName}" /&gt;
    &lt;/p:column&gt;
  &lt;/p:selectOneMenu&gt;
  </code></pre>