Bring back csv export

[sethsec]

I would love to have a csv export again. I have never seen the old one, but here are the fields I'd like to have:

Account, Principal Name, Principal Type, Policy Name(s), Policy Type, Privesc Methods Identified

[kmcquade]

Right on. Previously, this was generated as part of the Python (it would write a separate CSV file). I think there was also a UI option but I could be mistaken. I would prefer to not introduce it as another command line option, but it seems reasonable to add it as part of the UI.

Implementation notes: If someone wants to take this on, I would definitely welcome PRs that generate CSV exports with the data above. There is a var for iam_data that holds all of the Cloudsplaining data, which you can use to generate a CSV file.