Model 5 Tourbillon modifications

I modified a few parts from the original design and added one new one:

- split Frame b into two pieces held together with a 2.5mm screw. This makes it easier to print. I also a hex hole a little smaller so that it fits more tightly (T5a, T5b). T5b needs to be turned the other way up before you print it.
- reduced the diameter of the roller so that the pallet does not collide with it (T5d).
- adapted a sprocket from one of the other Tourbillon models, and added a hole for a grub screw (holy sprocket hex).

I've included a blender file which might help to understand how the pieces fit together.