Pages addon

Event needed for Page addon
Needs to be `$phpbb_dispatcher = $this->dispatcher = new \phpbb_mock_event_dispatcher();`

`$this->dispatcher` needs to be added to the arguments in `return new \phpbb\pages\entity\page($db, 'phpbb_pages');` below

`$this->dispatcher` also needs to be added to the arguments in any `return new \phpbb\pages\entity\page($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