Attempts to prevent ninja infections, body temperature fix, icon fix

Tweaks infections so that they are more readily apparent to the infected person during the early stages.

* Deals toxin damage more rapidly
* Fixes bodytemperature not rising to fever_temperature when infected.

Based on a (small) amount of testing on the dev server it seems that an infection of a single body part under the current settings was doing around 15 toxin damage over the hour or so it took to reach terminal stages. This is much lower than intended and has the potential to result in "ninja" infections where people have no idea that they are infected when suddenly they hit the terminal stage ("You can't feel your [X]!") and take massive toxloss.

Ideally the infection should be readily apparent with the patient having taken significant toxin damage, vomiting, etc, well before reaching such a late stage. I haven't done any testing with the new value though, yet.