Topic/plt 430

* Added **CouponIborFxResetDefinition** as an extension of **CouponDefinition** since the toDerivative method requires two sets of historical time series. 
* Added **CouponIborFxReset**.
* Implemented **CouponIborFxResetDiscountingMethod** for PV, PV sensitivity and currency exposure. 
This test should cover the three coupons: CPN_SAME_FIXING_DATES, CPN_FX_FIXED_FIRST, CPN_INDEX_FIXED_FIRST.