Edit Book: Show the filename of the currently edited file in the title bar. Fixes #1272543 [Enhancement : Book Editor - show file path](https://bugs.launchpad.net/calibre/+bug/1272543)
Edit Book: Fix extra 1x1 unused GIF image being created when saving and re-opening AZW3 files. Fixes #1272410 [Editing AZW3 book adds 1x1 pixel gray gif each time](https://bugs.launchpad.net/calibre/+bug/1272410)
Get rid of the unnecessary tracking of changes in the split view
Resize images in diff view when the view is resized