Provide a ranked source list (studies and trees) for historic synthesis releases

[jimallman]

We've talked about this before, just wanted to capture the request. This might be offered as a static page listing source trees/studies, but a tree collection for each release might be more useful.

[jimallman]

@jar398, please re-assign as needed.

[josephwb]

I believe I found these data: 4 python lists (plants, metazoa, fungi, and microbes, in that order) for each of the last three trees.