Topic/plat 6744

* Demo test for in-arrears products in **CouponInArrearsCalculationTest**.
* Calculations are wrapped in **CouponInArrearsCalculation**.
* Sensitivity calculators are implemented for **CouponIborInArrearsSmileModelReplicationMethod** and **CapFloorIborInArrearsSmileModelCapGenericReplicationMethod**. 
Could you add an example that uses the MUTLICURVE_FFS curve to match the OG-solutions examples?