Funding intervals and the Funding carry model

ArcDelta now reports each venue's funding interval and next settlement, and Labs has a new Funding carry model.

• Funding rates in the ArcDelta API now come with the settlement interval, the next settlement time and where these figures come from.
• A new request returns settled funding rates of every venue of an instrument.
• The next settlement time on OKX is no longer one interval too late.
• Funding carry forecasts the next-day average rate on each venue and shows what a position pays or receives per day and at the next settlement, with the annual rate on the venue's actual interval.