Log the JSON response on errors so that we can figure out what's going

wrong.  This will help diagnose #1364 which appears to be an
ORM_Validation_Exception, except the actual output is getting eaten by
the Organize SWF so we can't see it without snooping network traffic.

modules/rest/views/error_rest.json.php

@@ -1,2 +1,6 @@
 <?php defined("SYSPATH") or die("No direct script access.") ?>
+<?
+// Log error response to ease debugging
+Kohana_Log::add("error", "Rest error details: " . print_r($e->response, 1));
+?>
 <?= json_encode($e->response);