Shiv Particles Fix file

Fun little particle fix, proof of concept. Replace in your system folder (note, if you play online/multiplayer, this will cause a mismatch trying to join servers for now, so make backups)

Fixes:

-Adds alpha fade out to Flame Thrower primary fire effect, trails off a lot more smoothly now.
-Adds collision to the flames form the Flame Thrower so they no longer pass through geometry.
-Adds subtle quick fade out for most of the large sparks effects (lightning strike on rooftops for example) so they don't just vanish instantly, but I kept it very quick to replicate a hot spark burning out quickly. Looks a lot nicer.