Moving Account FKs to point to code field

The Peace Corps team uses account codes as their primary way of identifying projects. Pointing the Account foreignkeys on Campaign and Project to the 'code' field allows us to pull the code without having to do a table join.

This PR also includes a cleanup to get SirTrevor fields to serialize correctly.
Would it work if this was replaced with `return str(sirtrev)`? I don't think we need to parse and encode the data.