Fixes for @Aranclanos

Diseases now have a requires and a required_limb variable
if requires is 1 then it will run a check for required_limb (WHICH USES TYPEPATHS)

Reverts a turret change that git through into the pull for some reason

added some feedback messages in certain places

removed the hulk-like snowflake check that was really crappy anyways

Reworked a part of surgery/surgery_step.dm to use a switch