Added Sleep Mode Functionality for Lights

Sometimes, after an extended period of time, LEDs are failing on some devices. So I thought it would be nice, to add a sleep mode, for the lights. I've also made the interval and idle time configurable. Maybe at some point in the feature, this can be added in the GUI, but for now, it's only configurable in the config file.

PS: I've also added a standalone option, for a faster app launch (if the user knows, there is no server running).

Best regards Chris