button support

[sprintf]

support a mode where the car has a driver acknowledgement button

button related functionality

• enable / disable locally (settings) and remotely (from pit command)
• if button enabled, then flash display when message(s) ready
• hitting button will
• 1 : display pending message
• 2 : add the message that has been displayed to a list of acknowledged messages
• 3 : upon lap completion : notify the pits of all the messages the driver has seen

[sprintf]

rethinking this now. The button functionality shouldn't be so much of a tease.
we should expect all pis to have a button.
allow it to change video modes
allow it to ack a message.

in order to ack a message, then the ack system needs to wire itself in and take over the button for a short time ... say 30s. While it is connected, it's the only system that gets the button push. Oh... still need the button click sound.
If it toggles display modes then we would need to prevent it doing that when it is acking.
But we have nothing to toggle right now.