This needs to be a bit more careful for i18n, as we're extracting lower case strings in POWER_ON/OFF_ACTIONS so we get "reboot", "poweroff" etc translated.  This code tries to translate the humanised versions of "Reboot" etc, which aren't translated (they're case sensitive).  Another minor issue is that it should be "power off" in English.

I'd suggest changing the power manager constants to hashes of method names to user-friendly strings and iterate over key/value pairs.