Create GLUI classes.

Started on GLUI. Added the following classes:

- GLUITheme: When you create your GLUI you create a GLUITheme - a set of colours and fonts which can be given to a component to automatically style it. GLUI Components should accept a GLUITheme and set colours/fonts etc. appropriately.
- GLUIComponent: The superclass for all GLUI Components - this includes Buttons, Text Fields etc.
- GLButton: The button GLUI Component. You must define the onClick() method when you instantiate a GLButton. Currently does not allow texturing.
- ColorFormatException: Thrown when a dealing with invalid RGB hex codes.
- GLUIException: The superclass for all GLUI related exceptions.
- TestGLUI: The test window for GLUI Components - currently for development purposes only. Try running it to view existing GLUI Components.

The following classes exist in AWT but new versions have been written to add functionality which did not exist:

- Rectangle: Represents a rectangle.
- Point: Represents a point in 2D space (x,y).

The following classes exist in Slick but new versions have been written to add functionality which did not exist:

- Color: Represents a set of RGBA values which can be bound in openGL.

Changelog:

* Added color functionality to Font class - you can now specify a color in which to draw the text. Will later expand to formatting codes within text string.
  * Updated various classes in Main to use this new functionality.
* Moved Font class to glui package.
* Copied existing test font for use as default font - res/img/defaultFont.png