Enable flipping through preview images with keyboard arrows

[bourque]

Users are going to be using the web application to visually inspect many images. It would be convenient if they could easily navigate to next and previous images with the keyboard arrow keys intend of clicking a button with a mouse.

[bourque]

I believe @laurenmarietta has poked around at implementing this but doesn't quite have it working(?)

[laurenmarietta]

I tried this before I had any understanding of JavaScript, and then haven't gotten back to it sense.

I have a bit more confidence that I could figure it out now - or I would be happy to delegate out to someone else who wants to learn a little JavaScript!