Add classes to abstract Users and Courses

Can refuse a question (email the author)
Can modify question before validation

Course.class.php

@@ -53,6 +53,16 @@ class Course
     return $courses;
   }
 
+  public static function getCourse($id, $filename = "courses.xml")
+  {
+    $treeXML = new DOMDocument('1.0', 'UTF-8');
+    
+    if (@$treeXML->load($filename))
+      return new Course($treeXML->getElementById($id));
+    else
+      return null;
+  }
+
   public static function setCourses($courses, $filename = "courses.xml")
   {
     $treeXML = new DOMDocument('1.0', 'UTF-8');