Pages addon

Event needed for Page addon
`$this->dispatcher` needs to be added to the arguments in `return new \phpbb\pages\entity\page($db, 'phpbb_pages');` below on line 53

`$this->dispatcher` also needs to be added to the arguments in any `return new \phpbb\pages\entity\page($db, 'phpbb_pages');` you find in the following files:
1) tests/operators/page_operator_add_page_test
2) tests/operators/page_operator_delete_page_test