Rename Cube class to Pikachu
When I originally made this Cube class my goal was to create a textured cube but this became impossible with my current setup and I needed to implement a cubemap instead. As this hasn't been achieved yet, I only drew a textured square of Pikachu. This MR simply renames the Cube class and all references to Pikachu to allow the Cube class to be used for drawing an actual cube eventually.