MDL-21652 html_table rendering refactored

* class html_component does not exist any more
* class html_table rendered via html_writer::table()
* html_table, html_table_row and html_table_cell have public $attributes property to set their CSS classes
* dropped rotateheaders feature, should be added again after more research of possible ways (<svg> is not nice IMHO)
* dropped possibility to define CSS classes for table heading, body and footer - can be easily done and better done using just table class and context

question/type/questiontype.php

@@ -1144,7 +1144,7 @@ class default_questiontype {
             }
             $table->data[] = $data;
         }
-        return $OUTPUT->table($table);
+        return html_writer::table($table);
     }
 
     /**