Remote Power Down for Raspberry Pie 3 Model B+

This is a remote shutdown modification for the Raspberry PI 3 Model B+ that is using the stock Octoprint disk image. The circuit provides a ~25second time delay for the PI to boot and enable its external USB ports. Once booted, the power is locked in until the remote system shutdown is issued through the browser. Once the system shutdown starts, a approximate 25 second timer starts when the external USB ports are powered down. The 25 seconds allows the PI to fully park itself before removing a