Changes time series requirement in FuturesFunction back to MARKET_VALUE as ACTIV and BBG both have FieldMappings that convert names (e.g. Close, PX_LAST). This reinstates hts normalization
Removed requirement for InterestRateFutureSecurity's ExternalId _underlyingId to be not null
As Activ doesn't always provide the underlying, I moved spot requirement down to SpotFucntion