Finished sprite implementation
	modified:   geometry/Rectangle.cpp
	modified:   geometry/Rectangle.hpp
	modified:   geometry/Sprite.cpp
	modified:   geometry/Sprite.hpp
	new file:   geometry/SpriteSheet.cpp
	new file:   geometry/SpriteSheet.hpp
	modified:   geometry/geometry.hpp
	modified:   graphics/GlutHandler-main.c
	modified:   graphics/GlutHandler.c
	modified:   graphics/gl_utils.cpp
	modified:   graphics/gl_utils.hpp
	modified:   graphics/graphics.cpp
	modified:   makefile
	modified:   physics/Entity.cpp
	modified:   physics/Entity.hpp
Fixed sprite selection in SpriteSheet class
	modified:   geometry/SpriteSheet.cpp