Add account `type` to protocol

[travisby]

Howdy,

I just read through the spec and started playing with the bridge. I think it'd be neat if the account type was part of the spec, leading to different user interactions if it's a 401k vs a checking account vs a loan, etc.

Thanks for running this spec!

[edit] it looks like it gets defined in

simplefin.github.com/_data/sfindata.yml

Line 17 in 1447816

attributes:

[iffy]

We could add that. We'd need a somewhat exhaustive list of account types, I think, with "unknown" for everything else. It would probably work to look at account types defined in the OFX spec or similar.