calendar/validate

• isValidBusinessCalendar: Return true when calendar is a BusinessCalendar the business-day functions accept.
• isValidFiscalPattern: Return true when pattern is a valid FiscalPattern.
• isValidRollConvention: Return true when convention is a RollConvention that rollDate implements.
• isValidZoneBucketUnit: Return true when unit is a valid ZoneBucketUnit.