User-specified regional aggregation

[ssmithClimate]

It would be valuable for the user to be able to specify a regional aggregation for the tool to use.

This would be valuable in several circumstances: 1) to get a higher level view of the results, or 2) to be able to focus in on a specific region that a project have targeted (e.g., show South American regions, and aggregate the rest of the world into a few regions).