Suite of Small Test Pieces

[Update #2: I updated Flat Test to make it cleaner to print, and also a little more likely to curl on one corner.]

[Update #1: I uploaded a revised file #7 -- the caps on the little towers were off about 0.1mm.]

This suite of test models starts with a few very simple shapes, and then adds more complex models.

The purpose is to allow new 3D printer users to start learning with the basics and to produce models that allow them to focus on just a few potential problems at a time.

[Op