Placeholders for Bluray rips

Added placeholder Source/Worker plugins for ripping Bluray items.
Added placeholder iterator filter to accept only Bluray sources while
iterating directory contents.

lib/RippingCluster/Utility/BlurayDirectoryIterator.class.php

@@ -0,0 +1,9 @@
+<?php
+
+class RippingCluster_Utility_DvdDirectoryIterator extends FilterIterator {
+    public function accept() {
+        return true; // TODO Determine if the current directory item represents a Bluray source or not
+    }
+}
+
+?>