Support for optional flat list display of All Books

Here's the suggested change to support showing the All Books option as the default Split by First Letter listing or as a Flat list. Configurable in the same way as can be done for the Authors listing.

Also corrected an omission. The original All Books listing did not show an icon in the feed listing, to fix this I added the ALL_BOOKS_ID to the list of icon constants

And I made a change so that when you view the Book Detail popup, you don't get to see the ORIGINAL_EPUB copy in case it was present. It was already filtered on the regular title listings but still got shown in the popup. Since I see no use for this option I made the loop in getDatas skip these.