Implements Config and Logging plugins, tidies Main

Added Database and Flatfile plugin engines for both Config and Log classes.
Rewrote Main to make use of the new plugins.
Updated config file definitions to make use of plugins.

source/lib/Sihnon/Config/IPlugin.class.php

@@ -0,0 +1,29 @@
+<?php
+
+interface Sihnon_Config_IPlugin extends Sihnon_IPlugin {
+    
+    /**
+     * Returns a new instance of the Plugin class
+     * 
+     * @param array(string=>mixed) $options Configuration options for the Plugin object
+     */
+    public static function create($options);
+    
+    /**
+     * Loads all the configuration items from the storage backend
+     * 
+     * @param string $source_filename Filename of the source
+     * @param bool $scan Request that the source be scanned for content. Defaults to true.
+     * @param bool $use_cache Request that the cache be used. Defaults to true.
+     * @return RippingCluster_Source
+     */
+    public function preload();
+    
+    /**
+     * Saves the value of all configuration items back into the storage backend
+     */
+    public function save();
+    
+}
+
+?>