Add TradeStore and ReferenceDataStore

Remove CalendarStore
Move some tests to EventStoreTests
Refactor JsonProtocols
Add ReferenceDataTrait
Prevent storing of duplicates in EventStore
Merge pull request #13 from thoozaho/more-stores

Add TradeStore and ReferenceDataStore
Refactor Swaps and Position

Added CommoditySwapSpread. Added discounting. More tests.
Some caching and performance improvments.