Improved GuillotineBinPack

Added explicit copy/move constructor/operator
Added Expand method
Added Insert overloads (you are now able to query which rectangles were
inserted)
Made occupancy computation more precise
Overloaded methods taking a unsigned int pair with Vector2ui
Added conversions to A8 pixel format
Fixed pixel format conversion from A8 to RGB5A1
Added TODO
Added OpenGL support for pixel formats A8/L8/LA8