cable clamp library

Library for adding cable clamps to your project.

Stand alone, the library is not very useful as it lacks a way of mounting the clamps. This needs to be added externally. See cableclamp_usage.scad for an example.

See [cable clamps](https://github.com/x12a1f/rol/blob/master/doc/cableclamp.md) on github for more information on how to use and customize the clamps.