prepare for serial port based event logging
indent based reformatting of all C++ source files

added xcodeproj files
ignore all ~ files
ignore Builds directory
an IntervalTimer subclass to blink an LED

requires an LED pin identifier, plus on or on/off times in order to work.
base functionality for the IntervalTimer

an abstract class that handles all of the math & storage for the variables needed to record an interval,
and to perform an action when sufficient time has elapsed.
Add the new BlinkTimer for LED on pin 13.
switch boolean to bool
move showColon logic to displayDigit
new IntervalTimer class to flip the value of the specified boolean variable
use BooleanTimer to blink the colon
add xcodeproject bits