SAAS-382: Reimplement Storage Quota

Storing disk usage in cc_pref
Add/subtract filesize to/from disk usage total when a file is uploaded or deleted
TODO: Hook this into the ftp server

airtime_mvc/application/controllers/LibraryController.php

@@ -356,6 +356,7 @@ class LibraryController extends Zend_Controller_Action
 
             if (isset($file)) {
                 try {
+                    Application_Model_Preference::updateDiskUsage(-1 * abs(filesize($file->getFilePath())));
                     $res = $file->delete();
                 } catch (FileNoPermissionException $e) {
                     $message = $noPermissionMsg;