Consider changing contributor_aggregate_YTD

[cnlucas]

What we’re after

contributor_aggregate_ytd is per cycle if it's a Form 3 since 2000, but the field is the same for all other receipts where the field is actually per calendar year. This is a bit confusing and inaccurate for our users. We should consider having a separate field for cycle YTD. We should, if we can't do this, consider adding something to explain this issue.
https://api.open.fec.gov/v1/schedules/schedule_a/?two_year_transaction_period=2016&recipient_committee_designation=P&per_page=20&api_key=DEMO_KEY&sort=-contribution_receipt_date&sort_hide_null=false&sort_null_only=false

the form change information is here (thanks Dorothy!)

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