NEW:
- #204 Added https://biblionet.gr for Greek books.
- #212 Revised Greek translation.
- #214 Support "digest" authentication for Calibre
- #82 set a preferred author role in the book list
- Batch scanning "save" option.
- Performance improvements:
  - calculating number of books in complicated styles
  - image loading
  - Scrolling
  - Scrollbar-jump
  - Dragging the scrollbar simply shows the text-bubble for navigation.

FIXES:
- #207, #213, #216, #218, #220