Harmless and helpful diseases will no longer trigger medicalHUD

Any illness composed entirely of symptoms that are either harmless (coughing) or helpful (weight even) will be treated as a non-issue by medical HUDs.
One that includes a harmful but nonfatal symptom (vomiting) will trigger the traditional green sick icon.
One that includes a symptom actually capable of killing an infectee will trigger a new red sick icon.
Helpful symptoms have been ranked above harmless ones to facilitate a future "infected with something good" icon, though one is not included in this push.
Old diseases have been given HUD responses that match their capabilities (except for Fake GBS, which will register as fatal just to scare people)