Body temperature fixes and updates

Body temperature regulation is now based on species, and environmental
temperature now respects the air density when affecting living/humans.
This also fixes some bugs with heat/cold protection handling and
improves the way synthetic species body temperatures are handled to be
much more logical.

IPCs always gain temperature but cool down because of their environment.
When the heat transfer to the environment is reduced because of the lack
of air, this will cause IPCs to heat up.

As well, having an infection will increase your body temperature, and
body scanners now detect infections.

(cherry picked from commit cf5ff7e9922fc9e5f7569ec366833900cea89f2d)

Conflicts:
	code/modules/mob/living/carbon/human/life.dm
	code/setup.dm