Update worker code to the point that it can run.

Added plugin architecture for Worker functions, to support multiple
ripping engines.
Update worker script to use the new code.
Update Logger to output messages to console when running under the
worker script.

lib/HandBrakeCluster/Worker/IPlugin.class.php

@@ -0,0 +1,16 @@
+<?php
+
+interface HandBrakeCluster_Worker_IPlugin {
+    
+    public static function workerFunctions();
+
+    public static function rip(GearmanJob $job);
+    
+    public function evaluateOption($name, $option = null);
+    
+    public function callbackStdout($id, $data);
+    
+    public function callbackStderr($id, $data);
+}
+
+?>