Remove Menu::compact() in favor of putting an if-then clause in

menu.html.php.  This serves two purposes:

1) It's more efficient since we're doing less passes over the Menu tree
2) We're allowing themers to decide whether or not to show empty menus

modules/gallery/views/menu.html.php

@@ -1,4 +1,5 @@
 <?php defined("SYSPATH") or die("No direct script access.") ?>
+<? if ($menu->elements): // Don't show the menu if it has no choices ?>
 <? if ($menu->is_root): ?>
 
 <ul class="<?= $menu->css_class ?>">
@@ -21,3 +22,4 @@
 </li>
 
 <? endif ?>
+<? endif ?>