P0-A2: Part 463: Refactoring

I have finished the Gravity System improvements and refactoring.

I also attempted to merge the art scene that I recently created for the VR game with the main scene, but I had issues doing this.

They may be related to performance problems with merging two very complex scenes together. I will need to take a closer look at this at some point in the future. Eventually, I intend to have very complex static scenes for ships, cities, etc, and then less complex dynamic scenes for isolated structures and buildings.