Initial commit of Session/Authentication code

Plugin architecture with single Database-backed implementation.

source/lib/SihnonFramework/Auth/IPlugin.class.php

@@ -0,0 +1,23 @@
+<?php
+
+interface SihnonFramework_Auth_IPlugin extends Sihnon_IPlugin {
+    
+    /**
+     * Creates a new instance of the Auth Plugin
+     * 
+     * @param SihnonFramework_Config $config Config option to retrieve plugin configuration
+     * @return SihnonFramework_Auth_IPlugin
+     */
+    public static function create(SihnonFramework_Config $config);
+    
+    public function userExists($username);
+    
+    public function listUsers();
+    
+    public function authenticate($username, $password);
+    
+    public function authenticateSession($username);
+    
+}
+
+?>