Particle updates, minor fixes.

The 2021 updates just keep rollin'.

This time around the particle system has been given a moderate update. Several weapon effects have been improved for effect and readability.

Bullet impacts now render on terrain, as well as your mech's footsteps. Missiles and explosions give off clear pressure blast waves to let you know you've hit something.

Maps have been given a bump in the atmosphere with the addition of fog and particle effects. Rain, snow, dust are now all working again.

Lastly, I think I've fixed some of the resolution-rebuild headaches that some players have experienced.

I don't have any funny halloween meme-content this time around, but new mechs lurk on the near horizon.