Changed
* Improvements to the import from large mbox files with multiple labels
* Not allow to run multiple instances of the app or transfers at the same time
* Better handling and displaying of skipped messages
* Various enhancements of the import process related to parsing
* Cosmetic GUI changes
* Better error handling
Fixed
* Linux font issues - Fedora specific
* App response to the user pausing and canceling import or export
* Upgrade errors
