Helpers for publication start and end

[JayPanoz]

It could help implementers if Navigator could return whether a publication is at the start or the end in a reliable manner.

Although it’s possible to implement different strategies at the app level, we know it’s also difficult to do it for end since progression is never 100%, a position may be spread on 2 pages, etc. This is why the additional information Navigator gets privately could help determine these 2 states more reliably.

Use cases include:

• disabling navigation arrows while at start (left in LTR) or the end (right LTR);
• marking the publication as read
• Moving to the next publication in a series

[mickael-menu]

This is also something that we've been requested on mobile toolkits. I thought of adding information about the column index + column count of the current resource in the "moved" event.

Caveat: Many books actually end much before the end of the reading order. Here landmarks would be more useful.