Add a delay to Minibar's power button so that users must press and hold the power button for two seconds to turn sled power off

[isobering]

Today, we discovered three things:

• The rails on a Minibar Lite make good handholds
• When you grab a Minibar Lite by the rails to lift it off the sled, your thumb lands on the power button
• Minibar's power button toggles the sled power state as soon as it's pressed

As a result, it's extremely easy to power cycle the sled you're working on when you lift up a Minibar Lite to (for example) plug in a dongle.

We'd like to modify Minibar's power button behavior so it behaves like a normal PC power button. Ideally, the power button behavior would be:

• When the sled power is off, pressing the Minibar power button immediately turns sled power on
• When sled power is on, momentarily pressing the Minibar power button is ignored
• When sled power is on, pressing and holding the Minibar power button for two seconds turns sled power off