Parametric strandbeest in OpenSCAD

This is a customizable strandbeest designed completely from scratch in OpenSCAD, using only the [strandbeest linkage lengths](https://commons.wikimedia.org/wiki/File:Strandbeest_Leg_Proportions.svg) as a guide.

There are a number of strandbeesten available here on Thingiverse, but I perceived problems in all of them, such as: requiring support structure to print, asymmetrical joints, designs that haven't proven to be printable, too flimsy, too blocky-looking, or providing just STL files without CAD files for customization. So I set out to design my own strandbeest without these deficiencies. My requirements were:

* Designed completely in OpenSCAD
* No asymmetrical joints
* All extrusion profiles use graceful curves, no straight lines
* The widest leg segment (which I call a "bone", specifically bone "c" in the diagram) connects the central frame to the foot, for better stability
* All parts are printable without support
* All parts snap together, no glue or fasteners needed