ThreeJS visualization of dataset types

[matthewturk]

For three of the main types of data (AMR, unstructured, particle) we should have a simple ThreeJS visualization of the structure of a simple dataset. This would be a very straightforward addition to the paper and could largely be snagged from an export from widgyts.

I'd like to have octree as well, but tht poses some additional challenges.

[matthewturk]

Also, these will almost certainly need to be decimated or otherwise downscaled in resolution.

[matthewturk]

I included AMR.