Performance patch and bugfixing (V 1.0.4.8)

Changelog:
There were a lot of small changes in this one, but here are the highlights:
1. Performance is increased. I see a 2X framerate improvement on my computer, but ymmv.
2. We added 3 save slots and gave the save system one more look-over. Auto-saves are easier to access now, some players were getting confused and a couple overwrote a save file on accident. This should be much harder to do now.
3. There was a bug where the magazine disappeared on prestige under certain circumstances.
4. I looked through the backlog and fixed as many bugs as possible. So if you still see anything, let me know. Otherwise, let's assume that the game is bug free 😆

Notes:
I've been slowly working on some new features, but the churn was getting pretty big, so I wanted to get the performance patch out first. The next update should be much smaller (in terms of code changes), but more impactful on actual gameplay.