Pascaline

This is a remix of work done by [José Campos](https://www.prusaprinters.org/prints/28807-mechanical-calculator-modular-design) and [dvd71](https://www.thingiverse.com/thing:4395600)

Any of my changes were made for one of three reasons:
Aesthetics (Trying to make it look as much as a real pascaline as possible)
I loosened tolerances to reflect my current skill level.
I oriented parts as I would print them.

By the time I got to the third module, I'd created an "Alignment Tool" that would make sure everything was square and in the right position before placing the shaft. This really came in handy when orienting the dial, carry gear, and "spool".

My original plan was to find a brass strip of metal for the slider, but I was able to create one that fits a 4-module adder and could be printed in one piece.

I first learned about the pascaline while reading [Bit By Bit](http://ds-wordpress.haverford.edu/bitbybit/bit-by-bit-contents/chapter-one/1-7-pascal-and-the-pascaline/) in high scho