Putting small images in the submission legend (80 px as per @rowo's recs...

...), and linking to the large image. Closes #1072
Note that I want to change this [case statement](https://github.com/onaio/zebra/compare/1072_small_images?expand=1#diff-7870c60ea4bd6d23bd84fa0fdb5c2f92R96) to be a cond that works off of functions such as `image?`, but I don't want to do that until https://github.com/onaio/zebra/pull/1061 is merged in, because I have renamed all of those functions in there, and its going to cause a big merge mess.