Improvements:
- Preserve FITS keywords in sum stacked image or when history exist
- Check if the number of FITS can be stacked by Siril on the system
- Made command SEQCROP scriptable
- Redesigned all dialog windows to conform to GNOME guideness
- Improved ECC alignment algorithm
- Automatically detect GTK+ dark theme preference
- Adding a setting to activate image window positioning from the last session