Enhanced Countdown Timer

A new, significantly Enhanced Countdown Timer driver, inspired by the original Control4 driver 

1. Countdown units may now be ‘Seconds’, ‘Hours’ or ‘Days’ in addition to ‘Minutes’.
2. A specific time of day may be specified for triggering when ‘Days’ are used.
3. A new optional UI facility is provided to cancel the countdown and/or cycle the times again while running.  
4. A new programming command and a keypad connection are available to Cancel countdown.
5. UI feedback is provided when the countdown actually starts.
6. A new 'Countdown Cancel' event is triggered when the countdown is cancelled (instead of the normal ‘Countdown Off’).
7. A new 'Countdown Start' event is available.
8. By default, countdowns are restarted automatically upon Director reboot or driver update.  This may be modified via a property.
9. A new MINUTES_LEFT variable is continuously updated during countdown.
10. A new output CONTACT_SENSOR is activated when the countdown is running.

The driver is controlled by an Experience Button and/or a keypad button and/or programming to select a delay and start the countdown.  Several events are triggered at the start, the end and during the countdown itself.  A relay and a Contact Sensor output are also activated while the countdown is going on.