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/PluginFactory.class.php

@@ -0,0 +1,50 @@
+<?php
+
+abstract class HandBrakeCluster_PluginFactory {
+    
+    static protected $validPlugins;
+    
+    abstract public static function init();
+    
+    public static function getValidPlugins() {
+        return array_keys(self::$validPlugins);
+    }
+    
+    protected static function findPlugins($directory) {
+        $plugins = array();
+        
+        $iterator = new HandBrakeCluster_Utility_ClassFilesIterator(new HandBrakeCluster_Utility_VisibleFilesIterator(new DirectoryIterator(HandBrakeCluster_Lib . $directory)));
+        
+        foreach ($iterator as /** @var SplFileInfo */ $file) {
+            $plugin = preg_replace('/.class.php$/', '', $file->getFilename());
+            $plugins[] = $plugin;
+        }
+        
+        return $plugins;
+    }
+    
+    protected static function loadPlugins($plugins, $prefix) {
+        self::$validPlugins = array();
+        
+        foreach ($plugins as $plugin) {
+            $fullClassname = $prefix . $plugin;
+            if ( ! class_exists($fullClassname, true)) {
+                echo "Cannot load $fullClassname\n";
+                continue;
+            }
+            
+            if ( ! in_array('HandBrakeCluster_Worker_IPlugin', class_implements($fullClassname))) {
+                echo "$plugin does not implement the necessary interfaces\n";
+                continue;
+            }
+            
+            // Initialise the plugin
+            call_user_func(array($fullClassname, 'init'));
+        
+            self::$validPlugins[$plugin] = $fullClassname;
+        }
+    }
+    
+}
+
+?>