v1.28.0: New simulator and more

## New Features

- New Simulator (#531)
- Import Threadlist (#666)
- Export Threadlist in ZIP file (#664)
- Option to include SVG in ZIP file (#648)
- Break Apart and Retain Holes (#653)
- G-Code: option to alternate z-value (#659)
- New Stitch Plan Extension (#640)
- Optionally enable/disable ties (lock down stitches) (#619)
- Multiple Fill Underlays
- Additional Fonts (#683):
    * Geneva
    * DejaVu

## Improvements

- Better Algorithm for Satin Columns (#607)
- Better Algorithm for Fill Stitches (#606)
- Convert to Satin with Loops (#608)
- Adding '@ #' to all fonts (#680)

## Bug Fixes

- Fix Issue with Troubleshoot Pointer Position (#696)
- Inherit Styles (#673)
- Fix Color Palette Issues (#660)
- Preserve Aspect Ratio (#646)
- and more

## Under the Hood

- Namespaced Attributes (#657)
- Remove stub.py (#629)