Revised blood mechanics once more

Bleed rate now slows down over time (and the rate at which it slows is
based on wound count and blood level. Higher blood levels means it slows
down very slowly (high blood pressure) and as blood level drops, the
bleed rate slows faster).

Revised the formula for how bandages and medkits affect bleed rate.
Multiple bandages/medkits are required for slowing very fast bleeding.
Fixed an issue with unloading weapons

Cleaned up code a bit, only weapons that take magazines will be
unloadable now. Also prevented a console error with additional validity
checks.

Some other minor changes not worth talking about.