Close Packed Layers v2

I was having printing problems with the original Close Packed Spheres thing, but when I imported it into Sketchup it had too many holes for easy editing, so I redrew it. I also added more spheres (to the limit of build plate size on my smaller printer), collars between the spheres for strength, and an easily-removable base so that it doesn't need supports. I also am including a 50% model which could be printed in pairs and glued together, and a single sphere.