Added utility file iterator filters

Added SPL iterator filters to quickly and easily list visible files,
class files, and DVD source directories.

lib/HandBrakeCluster/Utility/DvdDirectoryIterator.class.php

@@ -0,0 +1,9 @@
+<?php
+
+class HandBrakeCluster_Utility_DvdDirectoryIterator extends FilterIterator {
+    public function accept() {
+        return is_dir($this->current()->getPathname() . DIRECTORY_SEPARATOR . 'VIDEO_TS');
+    }
+}
+
+?>