LP#1748006 Patron edit juv flag manual override

LP#1748006 Patron edit juv flag manual override

Allow staff to manually override the patron juvenile flag value
regardless of patron DoB.

Patch removes the ng-blur handler for dob and expire_date, which fires
too aggressively.  The dob handler is replaced with a $watch handler, so
the new and old value can be compared.  No watch is applied to
expire_date, since no code is currently fired when it's changed.

Change the log level of the "field changed" message from log to debug.

To test:

[1] Open a patron in the web staff patron editor.
[2] Apply a juvenile birth date (less than 18 years by default).
[3] Confirm the juvenile flag is automatically activated (if it wasn't
    already).
[4] Confirm it's possible to un-check the juvenile flag and save the
    patron.

Signed-off-by: Bill Erickson <berickxx@gmail.com>