data: Add ability for `IPaginationSource`s to specify how to get settings. The `IPaginationSource` has a new `getSettingAccessor` method that returns how to access settings values on items in the pagination source. A default accessor is also available, which uses standard attribute lookup. Also clean some stuff in `LazyPageConfigData`.

from piecrust.main import main


if __name__ == '__main__':
    main()