Universal Bottom Bracket Adapter

This is a configurable/parametric model for an adapter to convert one type of bottom bracket tool to another. The concept is based on rzschokke's SRAM DUM 44 to 49mm design as this seemed like a good way to make a plastic bottom bracket socket without concentrating forces on the four sides of a 1/2" square drive or six sides of a hex socket. I decided to build this in OpenSCAD to allow for different versions of the adapter to be built to support many combinations of existing sockets/tools and bottom brackets.

The parameters define settings for the socket that interfaces with your bottom bracket and a plug that would interface with an existing bottom bracket tool of another size you want to adapt. Here is a description of the parameters:

* socket_ID: Inner diameter of the socket that will fit over the bottom bracket. You will likely need to increase this diameter by 0.2-0.4 mm as printed circles tend to come out slightly smaller than defined in the model.
* socket_splines: numbe