Trying to address invisible defibs again

- Fix mistake in update_icon() proc that caused the defib to stay invisible when out of power
- Remove src. typecasting, formatting
- Try to clarify messages, notably since it leads to doctors believing they are treating unrevivable bodies when the ghost simply didn't re-enter body yet
Can do this as 
```dm
switch(charges/initial(charges))
    if(0.7 to 1) 
    if(0.4 to 0.6)
    if(0.1 to 0.3)
    if(0 to 0.1)
```
to remove the hardcoding