Changed the way image files are read
	modified:   geometry/Sprite.cpp
	new file:   graphics/bmp_utils.cpp
	new file:   graphics/bmp_utils.hpp
	modified:   graphics/gl_utils.cpp
	modified:   graphics/gl_utils.hpp
	modified:   graphics/graphics.cpp
	new file:   graphics/png_utils.cpp
	new file:   graphics/png_utils.hpp
Changed directory structure