ValuationDate type and attributes not properly defined

[tomhealey-icma]

type ValuationDate has multiple issues:

1. Attribute singleValuationDate and multipleValuationDates are not a date at all and do not have any date attributes. They actually hold actually an int attribute to define a number of business days.
2. fxFixingDate and fxFixingSchedule should not be defined as fx only.
3. Since ValuationDate is not a date but a set of attributes to define or adjust a value date it should be called something like ValuationDateSpecification