Reduced Material Protractor with Interlocking Fitted Arm

## Differences in Poikilos version
- The arm can print without supports on its back.
- The arm interlocks with the body of the protractor.
- The body has holes to reduce the use of material.
- (See also: Changelog)

Changelog:
## [ThingiVerse] - 2020-09-06
(Poikilos)
### Changed
- Import the original STL files into blend file.
- Move parts to the center (they were around 5500).
- Rotate the arm to print with less support material.
- Move the tab inward by 9mm so it actually goes into the slot.
- Add a ridge for matching the compass to an edge.
- Face the letters down for printing the body without supports.
- The "top" is now the flat side, such as in the naming of the blend
file's vertex groups.
- Reduce the thickness of the body from 8mm to 3mm.
- Include a 4.8mm axle and make the hole in the body 5mm for it (a bolt is no longer required).
- Add a 2mm hole to the new axle for an optional panhead screw.
- Make the tap narrower for less drag.
- Half the thi