Xeno blood rewrite + Xeno blood burns people

The tin says it all.

I am angry at:
-----------------
- the old coder who copy pasted blood code and used it again for xenoblood
- the coder who saw this mess and placed a snarky comment instead of fixing it.


I'm not 100% happy with how I handled adding xeno blood burning to trail_holder objects, but they're dodgy as fuck so I added another variable that will allow people to check what type the trail is, since all trail_holder objects are the same typepath regardless of being blood or xeno blood, etc.