Bug 26597: Transfer informations from guarantor when adding a guarantor to an existin...

Bug 26597: Transfer informations from guarantor when adding a guarantor to an existing patron

When creating a new guarantee from the guarantor, the preference PrefillGuaranteeField dictates some fields to be transfered from guarantor to guarantee. This patch makes it so those informations are also transfered when adding a new guarantor relationship to an existing patron.

To test:
1) Apply patch
2) Search PrefillGuaranteeField preference and make sure some fields are selected
3) Select a user that can have a guarantor
4) In the edit form, click on 'Search to add' in 'Patron guarantor' fieldset
5) Choose a patron who has at least one of the fields in 1) set
6) Click 'Select'
7) Confirm guarantee's information is filled from the guarantor's record
8) Check that any preexisting information is not overwritten

Signed-off-by: Sally <sally.healey@cheshiresharedservices.gov.uk>
Signed-off-by: Emmi Takkinen <emmi.takkinen@koha-suomi.fi>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>