Bug 14782: Add possibility to search patrons using the username (userid)

Bug 14782: Add possibility to search patrons using the username (userid)

This patch makes it possible to search for users using the username (userid / login name).

To test:

- Apply patch
- Do searches from Home > Patrons
- Search after a full username or parts of a username with Search fields = Standard and Search fields = Userid
- Perform the searches from the top bar (expand with [+]) and from the "Filters" part at the left
- Make sure that other searches behave as before

Signed-off-by: Joonas Kylmälä <j.kylmala@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@unc.edu.ar>