Undo divide chapters to pages in master branch

This PR reverts the code back to a state it was before the Initial changes for splitting chapters to pages commit because the commit was moved to the dev branch.

Splitting chapters to pages doesn't work with all books, on some books the text disappears leaving a blank page.

There are a few small changes that need to be done to make some functionality work when splitting chapters to pages:

returning to the current position when going back from other view (like word definition);
returning to an anchor when going back from the endnote;
etc.

And also maybe we should add a setting to allow user to choose whether to split chapters to pages or not?

babluboy / bookworm