Added per series settings page/tab & visibility + sort option for series list page

Not proposing this gets used as-is, but intended as a POC (one I'm deploying on my production site)

Using the settings-api.php class by Tareq Hasan I implemented a per-series settings tab where an admin can change the sort order for the series list (on the front-end) as well as choose to hide upcoming (future) posts.