v0.4.1

• Added new predefined shapes: half circle, 2D ring, half 2D ring, 3D ring, half 3D ring and c-shapes.
• Included new examples.
• Implemented generic procedures get_Xc(), get_Xg(), and get_Wc().
• Added cmp_degree().
• Designed a logo using ForCAD.
• Various improvements and bug fixes.