Bug 16316 - Limit patron search to surname

Bug 16316 - Limit patron search to surname

This patch makes it possible to limit a patron search to
search just for surnames.

To test:
- Apply the patch
- Add two patrons, called e.g. "John Doe" and "Doe John"
- Go to Patrons in the Intranet
- Make sure you have selected "Search fields" = Standard
- Search for "john" and verify both patrons show up
- Search for "doe" and verify both patrons show up
- Set "Search fields" = Surname and search for "john".
  "Doe John" should show up, but not "John Doe".
- Set "Search fields" = Surname and search for "doe".
  "John Doe" should show up, but not "Doe John".

Update: Revised the last point in the test plan.

Sponsored-by: Alingsås Public Library, Sweden
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>