IR Sensor Simulator Created

IR Sensor Simulator created, ready for code review.
Also added Mac auto-generated file to .gitignore list.
Code Review Changes (Comments improved)

Comments improved slightly to clarify what "orientation" means, and
minor changes per code review.
Merge pull request #1 from MarsRobotics/IRSensorSimulator

IR Sensor Simulator Created and code reviewed. Probably obsolete due to NASA rules changes.