new validator: dateRestrictionValidator

[Gabrielle Crawford]

Hi,

I'd like to add a new validator. My proposed name is 
DateRestrictionValidator, other suggestions welcome. This would support 
attributes like:

invalidMonths - example: dates in April are invalid
invalidDaysOfWeek - example: Saturdays and Sundays are invalid
invalidDays - example: 12-25-06 and 1-1-07 are invalid

The exact api's will be discussed further as the implemenation is worked 
out.

Does anyone oppose this or can I open an issue?

Thanks,

Gabrielle