Add column for what dataset an activity has come from

[Bjwebb]

The dataset name looks something like undp-abw, and is useful because people can look that up on the registry to find the url and other info https://iatiregistry.org/dataset/undp-abw

The data that iati-tables loads via iatikit has filenames named with the dataset (e.g. undp-abw.xml), so we should be able to get it from there.

I think we possibly want to add this as a column to every table.

[stevieflow]

I agree that this would be really useful

[tillywoodfield]

Column dataset has now been added to all tables