Add CLI utility to index pages with a `note`/`suggest_delete` meta

[Mark-H]

A CLI utility like php docs.php needs_attention should write a JSON file (or similar data structure) to a predefined location (perhaps needs_attention.json in the root of the doc source) and contain both the page name/link and the note so a special meta page can be added that lists pages needing attention.

[Mark-H]

This is indexed in the navigation cache, fairly easily available through the NavigationService. Needs to be outputted somewhere now :)