Deferring multiple split articles/pages

[robertjlee]

Currently, when a paste-up article does not fit onto a page, it is split onto the next available page.
Only one article can be split, and it is split only to the next page.

This does not reflect how this feature is typically used by newspapers, who often have multiple articles split in order to show more leaders on the first page, with detail delayed much later in the paper (so page 2/3 are for the more important stories that didn't make the front page).

We should keep the existing behaviour as an option, as it provides a good reading order. But we should allow deferring of more than one article, and provide options for the minimum page for deferred articles to be set onto. In this mode, it should be preferable to begin as many permitted articles as possible on their declared minimum page.