this release changes:
- disclaimer: breaking file format compatibility
- more shape types (curves, ellipse with foci)
- feature: new eraser type: split strokes
- feature: autosave
- reduced handwriting latency
- improved selector
- improved undo / redo system
- Xournal++ file import: drawn shapes are now imported correctly
- UI tweaks
- bug fixes
- a lot of code refactoring