LP#1361266 Patron self-registration form accepts date of birth in wrong format

LP#1361266 Patron self-registration form accepts date of birth in wrong format

This patch applys some basic javascript to validate that a date entered is
at least in ISO 8601 format.  This prevents someone from entering "cupcake"
or 55/66/6666 as a valid date of birth by validating the stgu.dob input
at the time of submission.

Signed-off-by: Michael Peters <mpeters@emeralddata.net>
Signed-off-by: Josh Stompro <stomproj@larl.org>