Bug 19916: Add keyword and standard ID fields to acq external search

Bug 19916: Add keyword and standard ID fields to acq external search

To test:
1 - Add an order from external source
2 - Note you don't have keyword or standard ID fields
3 - Add a catalog record from Z3950, note those fields are there
4 - Apply patch
5 - Check acq and note you do have those fields
6 - Do some searches to verify they work as expected

Signed-off-by: Maksim Sen <maksim.sen@inlibro.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>