Add callbacks to dashboard portlet rendering

In some cases, we might want to change portlet attributes
before rendering it, or even update HasResults attribute
after the portlet has been rendered.

This patch adds callbacks before and after rendering
portlets.

share/html/Dashboards/Elements/ShowPortlet/dashboard

@@ -77,6 +77,10 @@ Abort("Possible recursive dashboard detected.") if $Depth > 8;
 <%perl>
 local $session{CurrentUser} = $session{ContextUser};
 for my $portlet (@panes) {
+
+    $m->callback(CallbackName => 'BeforeComponent', Dashboard => $Dashboard,
+        HasResults => $HasResults, Portlet => $portlet, ARGSRef => \%ARGS);
+
     $m->comp($portlet->{portlet_type},
         Portlet    => $portlet,
         Rows       => $Rows,
@@ -86,6 +90,10 @@ for my $portlet (@panes) {
         Depth      => $Depth + 1,
         HasResults => $HasResults
     );
+
+    $m->callback(CallbackName => 'AfterComponent', Dashboard => $Dashboard,
+        HasResults => $HasResults, Portlet => $portlet, ARGSRef => \%ARGS);
+
 }
 </%perl>