Added basic material support.
Made small optimization to opengl interfacing methods.

Added classes:
	IGE.Graphics.Material

Added methods:
	IGE.Graphics.OpenGL.GL.ColorMaterial(FaceName face, ColorMaterialMode mode)
	IGE.Graphics.OpenGL.GL.Material(FaceName face, MaterialParamName pname, float param)
	IGE.Graphics.OpenGL.GL.Material(FaceName face, MaterialParamName pname, int param)
	IGE.Graphics.OpenGL.GL.Material(FaceName face, MaterialParamName pname, float[] param)
	IGE.Graphics.OpenGL.GL.Material(FaceName face, MaterialParamName pname, int[] param)