Bug fixes and performance improvements.

- Bug fixed that could make the app crash when entering non existing line reference in second column.
- Bug fixed that could happen when selecting "Display rational fraction".
- New Preferences option to highlight all calculated cells.

- Bug fixed that could make the app crash when entering non existing line reference in second column.
- New Preferences option to highlight all calculated cells.

- Bug that could prevent cell editing is fixed.
- New calculated cells highlighting.

Version optimized for iOS 15.

Minor user interface optimizations.

Minor user interface optimizations.

Cells used in calculation are now highlighted.

CSV files are now automatically opened by MiniXL.
Minor user interface improvements.