FEAT node images

[jimtobias]

I can only hope I'm doing this right....

I'd like to be able to load different images for nodes. (Not that I hate circles!) For the purpose of building policy visualizations, it's be great to, say, have an image for housing, another for healthcare, etc., and have them grow/change color/change fill % or even change to another image, based on the usual dynamics. Think of this as an interactive infographic.

[1000i100]

Why not, i was thinking, where to put this feature in the UI ?
But with #43 I think i know where to add it.