Version 0.4.1

Fixed design of the race track system for 1/24 to 1/32 scale RC cars.

• Fix a computation issue on the number of notches for the straight barrier holders (when the length is a multiple of the normal size)
• Improve the design of the U-turn barrier holders by adding a pocket to prevent round edges on the slot near the tower
• Dispatch the "special" shapes into more appropriate files (arch and connector)

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Notes:

• Import from the repository jsconan/things
• Extract of the pull request jsconan/things#48

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Pull requests:

• Feature/import from repo things/version 0.4.1 by @jsconan in #10
• Release 0.4.1 by @jsconan in #11

Full Changelog: 0.4.0...0.4.1