v0.6.17 - Under-the-hood Improvements

This release adds a feature to manage features specific to a certain Borg version and improves logging:

It also fixes an encoding bug that occured in the Extract-dialog on packaged macOS apps.

• Get borg version and path on startup. Link to log folder. (#247)
• Add helper class to manage Borg version and supported features. (#250)
• Correctly set environment encoding (pyinstaller issue). Fixes #220