Added ability to edit an element on the rearrange page

Increased the Moodle version required as this feature
uses the AMD module 'core/fragment' which was introduced
in 3.1.

db/services.php

@@ -0,0 +1,42 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Web service for mod customcert.
+ *
+ * @package    mod_customcert
+ * @copyright  2016 Mark Nelson <markn@moodle.com>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+$functions = array(
+    'mod_customcert_save_element' => array(
+        'classname'   => 'mod_customcert\external',
+        'methodname'  => 'save_element',
+        'classpath'   => '',
+        'description' => 'Saves data for an element',
+        'type'        => 'write',
+        'ajax'        => true
+    ),
+    'mod_customcert_get_element_html' => array(
+        'classname'   => 'mod_customcert\external',
+        'methodname'  => 'get_element_html',
+        'classpath'   => '',
+        'description' => 'Returns the HTML to display for an element',
+        'type'        => 'read',
+        'ajax'        => true
+    ),
+);