Improve page size so this can be set and persist

[brendanheywood]

At the moment when viewing the report at /mod/checklist/report.php you get a page size of 30. This can be overridden using a query param but this is lost when you click on anything. Some idea:

• if it is set as a query param and you click or save forms then pass the value around to persist it temporarily
• have an admin option to override what the page size it, either at the site level or at the module instance level

[davosmith]

Adding an admin setting to control this would be fairly easy to do (but still requires an hour or so of work to add, including the required Behat test(s) to check it is working consistently across all supported Moodle versions).

Persisting the value is also fairly easy to do (although, at that point, I'd probably also want a form to set it on the page, rather than just knowing what URL param to set).

Either way, I might get around to looking at it some day; I'm more likely to review + merge a patch, if someone else writes the code ...