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`.

[pytest]
norecursedirs = .* _darcs CVS .svn .git .hg *.egg-info dist build node_modules venv tmp* {args}