Turret Joint

**Note: ** After building this, I learned that it was essentially invented in 1999 as expressed in this [patent](https://patents.google.com/patent/US20010002964A1/en) by Se-Kyong Song, Dong-Soo Kwon, Wan Soo Kim. This joint should really be called the "Song Kwon Kim" or SKK joint in honor of them. However, "turret-joint" better captures what it actually is shaped like. Their patent has since lapsed, so you need not worry about patent infringement.

This is a new kind of [joint](https://github.com/PIFAH/turret-joint) which allows multiple members to come together at a single point with some flexibility in their angles. This allows us to make a strong joint for implementing irregular space frames or robots constructed from linear actuators.



**NOTE**: My initial testing with moving actuators suggests that although the joint works, it is quite "frictiony" when printed on the Fast setting on a Replicator 2---which makes sense because it is visibly striped and rough. However, to