Added both Windows friendly Mac OS X handling & Error windows to
GameEngine

In addition...
* Added ErrorWindow in order to display errors.
* Added error.png to go along with each ErrorWindow.
* Added MacOSXEventHandler to handle Mac OS X Events.
* Updated the gitignore.
* Added a new constructor in ByteColor
* Added tabbed spacing in GamePanel and removed the error println.
* Added security to Unsigned's mutators, as well as minor fixes