Spiritus Astrum [P0-B13]: p1535: Towards Early Access

The modelling improvements and changes are essentially done, for the moment.

I have fully integrated the art changes with the game, and fixed some issues that occurred.

I have also spent some time improving the AI enemies, and making other improvements, etc, to the game.

In addition, I have tested the campaign with the new artwork, and fixed all issues that I discovered.

The next goal is to add more checkpoints/save points to the story missions in the game, and test them.