Date Selector restrictions improvement

Currently the date selector field can be set to restrict past dates, but there isn't a way of restricting future dates. It would be good to have the option to enable, exactly like the current option, but to restrict future dates. This would be helpful for all the forms that ask for Date of Birth, or other past dates (date employment started, date moved into location, date something was issued) - which is quite common in a lot of forms.

It would be even better if you could set the value of restrictions say "restrict after X date" where X could be "today" or another form field or workflow variable.