KDjVu:
* Fix the cache handling to behave sanely in 90 and 170 degrees rotation
* Implement the threaded generation (the API is already ok)
* Annotations:
  - Read the missing properties, if possible
  - The default font size is quite small compared to the usual DjVu page sizes,
    what to do for this?
* Read the metadata in the document (like year, booktitle, editor, author, etc)
  stored as annotations