MDL-27490 Implement a manage question behaviours admin page

While doing this, I found various bugs in the manages question types admin page, and so fixed them, and updated the code
there to use $OUTPUT and html_writer.

AMOS BEGIN
 MOV [cannotdeletemissingqtype,admin],[cannotdeletemissingqtype,question]
 MOV [cannotdeleteqtypeinuse,admin],[cannotdeleteqtypeinuse,question]
 MOV [cannotdeleteqtypeneeded,admin],[cannotdeleteqtypeneeded,question]
 MOV [deleteqtypeareyousure,admin],[deleteqtypeareyousure,question]
 MOV [deleteqtypeareyousuremessage,admin],[deleteqtypeareyousuremessage,question]
 MOV [deletingqtype,admin],[deletingqtype,question]
 MOV [numquestions,admin],[numquestions,question]
 MOV [numquestionsandhidden,admin],[numquestionsandhidden,question]
 MOV [qtypedeletefiles,admin],[qtypedeletefiles,question]
 MOV [uninstallqtype,admin],[uninstallqtype,question]
AMOS END

question/behaviour/interactivecountback/behaviour.php

@@ -64,6 +64,10 @@ require_once(dirname(__FILE__) . '/../interactive/behaviour.php');
 class qbehaviour_interactivecountback extends qbehaviour_interactive {
     const IS_ARCHETYPAL = false;
 
+    public static function get_required_behaviours() {
+        return array('interactive');
+    }
+
     public function required_question_definition_type() {
         return 'question_automatically_gradable_with_countback';
     }