More descriptive error messages when trying to clone husks

Created by: 9600bauds

+- tweak: "Trying to clone a husk now provides a more informative error message, rather than the generic 'mental interface failure'. This message also tells you if the dead guy can still rejoin their corpse, so you can try to clone a husk before attempting a head transplant and know you're not wasting your time on someone that already logged out."

Tested decently, seems OK