Updating the UAV IO Library to add support for a 4th debug led

Signed-off-by: Dominic Baratta <dbaratta@buffalo.edu>
Adding support for button inputs on Port A. These are triggered by a
MEDIUM level interrupt.

Signed-off-by: Dominic Baratta <dbaratta@buffalo.edu>
Updating UAV IO Library to handle interrupt based inputs on PORT A

Signed-off-by: Dominic Baratta <dbaratta@buffalo.edu>