Add "Reload preview" button to chapter-processed book Manager page
As agreed in #807 (closed), users need reload chapters in bulk.
Dev tasks:
-
Refactor the buttons on the left-hand side the bottom bar, in the order shown below. -
Style "reload preview" button the same as "submit" button. -
On the files tab, reorder buttons "submit" and "reload preview" so it's the same as the book manager