Full screen image comparisons

[RunDevelopment]

Add a little button that allows users to compare images in sort of full screen mode. This may be implemented as actual full screen or just the whole document viewport.

[joeyballentine]

I was thinking of basically copying YouTube. A little bar at the bottom with a Fullscreen button, a "larger area" button, and maybe a button to center the image, and maybe a button to toggle between comparison states (0% / 100% slider values)