Build on work by @bendoh merged in f96afe53 and implement two paging options as toggles in the UI. Also makes the approach to applying the various paging types more modular and a bit easier to follow.

Lastly, WP coding standards. There's lots to clean up, so I only dealt with those bits I actually touched in the aforementioned work.

specifying page count

Basic autopaging functionality. Splits over two pages, includes an option to disable. Filter exists to modify supported post types.