Updates framework to support automated framework subclasses

All framework classes have been renamed to use the SihnonFramework_ prefix.
The class autoloader now looks for subclasses of the framework classes in the Sihnon_Lib directory, and
automatically creates them if they don't exist. The autoloader correctly creates interfaces and abstract
classes as needed, by using reflection to check the type of the parent class.
All references to classes within the framework now use the Sihnon_ prefix.
The PluginFactory supports multiple scan directories, and will search both the framework and subclass class
tree to find candidate plugins.

source/lib/SihnonFramework/Cache.class.php

@@ -0,0 +1,62 @@
+<?php
+
+class SihnonFramework_Cache {
+    
+    protected $config;
+    protected $cache_dir;
+    
+    public function __construct(Sihnon_Config $config) {
+        $this->config = $config;
+        $this->cache_dir = $config->get('cache.base_dir');
+        
+        if (is_dir($this->cache_dir)) {
+            if ( ! is_writeable($this->cache_dir)) {
+                throw new Sihnon_Exception_InvalidCacheDir();
+            }
+        } else {
+            if ( ! Sihnon_Main::mkdir_recursive($this->cache_dir)) {
+                throw new Sihnon_Exception_InvalidCacheDir();
+            }
+        }
+    }
+    
+    protected function cacheFilename($source_filename) {
+        return $this->cache_dir . sha1($source_filename);
+    }
+    
+    public function exists($source_filename, $ttl = 3600) {
+        $cache_filename = $this->cacheFilename($source_filename);
+        
+        // Check to see if the file is cached
+        if (!file_exists($cache_filename)) {
+            return false;
+        }
+        
+        // Check to see if the cache has expired
+        if (filemtime($cache_filename) + $ttl < time()) {
+            // Delete the cached item
+            unlink($cache_filename);
+            return false;
+        }
+        
+        return true;
+    }
+    
+    public function store($source_filename, $content) {
+        $cache_filename = $this->cacheFilename($source_filename);
+        return file_put_contents($cache_filename, $content);
+    }
+    
+    public function fetch($source_filename, $ttl = 3600) {
+        $cache_filename = $this->cacheFilename($source_filename);
+        
+        if (!$this->exists($source_filename)) {
+            throw new Sihnon_Exception_CacheObjectNotFound($source_filename);
+        }
+        
+        return file_get_contents($cache_filename);
+    }
+    
+};
+
+?>