Prevent future dates of birth in patron editor

Prevent future dates of birth in patron editor

The patron editor form allowed staff to enter a date of birth that takes
place in the future. While it is theoretically conceivable (hah) that
a library might register patrons that have yet to be born, it is
unlikely enough that we will not even assign this behavior to an
org-unit setting, but we will take the bold move of using a regular
expression to prevent a future dates of birth at all.

Note that if a library system travels into the past, this will cause all
sorts of problems in the patron editor interface (not to mention
overdues). Please do not mix Evergreen and time travel.

Signed-off-by: Lebbeous Fogle-Weekley <lebbeous@esilibrary.com>
Signed-off-by: Dan Scott <dan@coffeecode.net>