Rather than moving the themeroller and all of its associated files

into each theme.  I chose to create methods Theme_View::file($path)
and Admin_View::file($path).  These methods check for a theme override
file in the theme and return a link to it if it exists.  So to
override the themeroller files. just create a lib/themeroller in the
theme and the files will be picked up.

core/libraries/Admin_View.php

@@ -45,6 +45,11 @@ class Admin_View_Core extends View {
     return $absolute_url ? url::abs_file($arg) : url::file($arg);
   }
 
+  public function file($path) {
+    $theme_path = "themes/{$this->theme_name}/$path";
+    return url::file(file_exists($theme_path) ? $theme_path : $path);
+  }
+  
   public function display($page_name, $view_class="View") {
     return new $view_class($page_name);
   }