gtidfinity circle fill

This is a minor modification to [gridfinity-rebuilt-openscad](https://kennetek.github.io/gridfinity-rebuilt-openscad/) to add a nested circle infill, in answer to a request on https://old.reddit.com/r/gridfinity/comments/17v0zdy/looking_for_a_gridfinity_bin_similar_to_this/

see the [gridfinity-rebuilt-openscad](https://kennetek.github.io/gridfinity-rebuilt-openscad/) website for more complete information.

gridfinity-rebuilt-openscad is released under the M.I.T. license.
More [documentation](https://github.com/Stu142/Gridfinity-Documentation)


To use, download all three .scad files, put them in the same folder, and open `gridfinity-circle.scad` with the OpenSCAD app.


In the file `gridfinity-circle.scad` the code:

//circle infill.
intersection(){
translate([-circleDiameter*overlapPercentage*20,-circleDiameter*overlapPercentage*7,0])circleFill();
rounded_rectangle(gridx*length-0.5005-d_wall*2, gridy*length-0.5005-d