[PLAT-6444] Added visitor for SwapFuturesPriceDeliverableTransaction
[PLAT-6444] Corrected error message when non-DSF is passed in
[PLAT-6444] Added support for DSF and refactored code
[PLAT-6444] Refactored conditional blocks as per code review
[PLAT-6444] Renamed variable and formatted method arguments
Merge pull request #41 from OpenGamma/topic/PLAT-6444

Topic/plat 6444