Disc Crv

Key Disc Crv in ImpYC Forc refers to the riskless discounting yield curve associated with the source currency.
It is typically an OIS curve, produced by market data represented through an object of type Yield Curve Ois
If omitted, it is assumed equal to the Mkt Crv, in which case the resulting forecasting curve trivially equals the known market curve.
Expects an object of type Yield Curve.