Make it easy for people who want a Previous page button on the quiz attempt UI

In Moodle 2.x, we simplified the attempt quiz UI as much as possible. In particular we removed two buttons:

1. A previous button to get back to the previous page.

2. A 'Save without submitting button' (since clicking next saves everything).

I still think that, on balance, these are usability wins.

There are, however, some situations where these would be useful. For example, in a quiz where students are expected to answer long essays, then 'Save without submitting button' (perhaps better called 'Save changes') would be a good idea.

While I don't want to add these buttons to the standard quiz UI, and I don't want to add more setting to the quiz form, I am wondering whether it would be worth adding the necessary code to the renderer, so that people who do want to customise the UI in this way can do so really easily.

for example, a theme might only need to override

    public function save_changes_button($show = false) {

like

class theme_overridetest_mod_quiz_renderer extends mod_quiz_renderer {

    public function save_changes_button($show = true) {

        return parent::save_changes_button($show);

    }

}