Fix error when 0 (Sunday) is used as WeekDayNumber in HolidaysDefinition.json

[albertospelta]

Fixes a Wrong configuration in HolidaysDefinition error when 0 (Sunday) is used as WeekDayNumber in HolidaysDefinition.json.
This error has been reported in sql-bi/Bravo#766

This error happens, for example, for Mother's Day holiday celebrated in the United States on the second Sunday in May.

{
  "IsoCountry": "US",
  "MonthNumber": 5,
  "DayNumber": 0,
  "WeekDayNumber": 0,
  "OffsetWeek": 2,
  "OffsetDays": 0,
  "HolidayName": "Mother's Day",
  "SubstituteHoliday": "NoSubstituteHoliday",
  "ConflictPriority": 100
},

[marcosqlbi]

Originally, 0 was supposed to be the "not defined" state. However, because Sunady is defined as 0 (and we cannot change it now!) we rely on the priority of the conditions. For example, if MonthNumber is 92 (which is not supported), we end up using Sunday as the definition of the weekday.
I would add these conditions to proceed with the code of this case:

• MonthNumber must be in the range 1..12
• OffsetWeek must be <> 0
• DayNumber == 0