18650 Case x1 x2

This is a derivative of [18650 Case](https://www.thingiverse.com/thing:5348242) by Nurik98. These boxes allow safely storing 18650 batteries. They are meant to be functional, quick and easy to print with the smallest amount of filament.

Compared to the original case, I made the cap slightly thicker in the middle for a better grip, and a x1 variant for storing only one 18650 battery.