EX-Rail Feature request: Add power on/off events and the ability to query power status

Hi,

I would like to be able to query and react to the power status of my command station. E.g.

```
ONPOWER(mode)
    IFPOWERON()
        SET(POWER_LED)
    ENDIF
    IFPOWEROFF()
        RESET(POWER_LED)
    ENDIF
DONE
```

Would this be possible?