Version 1.7.0
* Added support for exporting and importing ZIP files.
  Uses the Zip4j library to support ZIP AES encryption.
* Fixed a bug where the XML importer was not
  restoring the scrollbar threshold preference.
* Fixed a bug in updating the scrollbar thumb where adding or removing text at
  the bottom of the note would update the thumb's size but not its position.
* Fixed a bug where a Clean import would silently do nothing
  if there were no user-defined categories prior to the import.
