Bitcoin two face

This has been fully remodeled inspired by karilawler version.

The changes include:
- Simpler polygons geometry in termos of the 'B' and groves around it resulting on faster prints.
- 3.5mm thickness with 0.8mm groves
- 40mm diameter
- 2 sided

The result shown in the pictures are using the following settings in Cura 4.4:

- Layer Height: 0.2mm
- Line Width: 0.4mm
- Wall Thickness: 1.2mm
- Wall Line Count: 3
- Bottom Layers: 9999
- Infill 100%

- Print Speed: 60 mm/s
- Wall Speed: 45mm/s
- Top/Bottom Speed: 25mm/s
- Initial Layer Speed: 15mm/s

I used an override between layer 6 and 12 to speed up the filling part of linear layers:
- Outer Wall Speed: 45mm/s
- Inner Wall Speed: 55mm/s
- Top/Bottom Speed: 70mm/s

These settings result on my printer 28mins for a single coin, around 2h30 for 6 coins and Cura predicts it will take around 6h for 15 coins.