Update to version 0.19.0

This update includes:

- A few minor changes under the hood I made while testing out various Ren'Py features and plugins I wrote. 

- The use of a sprite sheet for the robots and parts of the menu. Ultimately I don't think it's super useful for most Ren'Py games but it was a good test.

- Minor changes to how the robots are displayed.

- Upgrade forms for nearly every robot. At first this was just adding a few to get a really big sprite sheet, but it turned into a bit of a project. There's now 41 robots that can be unlocked and may the lord have mercy on my soul.