Bug 15656: Move guarantor/guarantees code - GetGuarantees

Bug 15656: Move guarantor/guarantees code - GetGuarantees

2 subroutines of C4::Members deal with guarantor/guarantees:
GetGuarantees and GetMemberRelatives.
Since we already have a Koha::Patron->guarantor method, it makes sense
to move these 2 subroutines to this module.

This first patch deals with GetGuarantees.

Test plan for the entire patch set:
1/ Create 5 patrons A (adult), B (child), C (child), D (child), E
(child), F (adult)
2/ Add relation between them: A is father of B, C and D.
E does not have a guarantor
F does not have guarantees
3/ Check some items out for all of these patrons
4/ On the "Check out" and "Details" tabs, you should not see any
differences with these patch applied : The "Relatives' checkouts" tabs
should list all of the guarantor/guarantee/siblings checkouts

Note:
$template->param('C' => 1);
I have not found any reference of this 'C' in the template.
It seems it's an old c/p from members/memberentrygen.tt

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Brendan Gallagher brendan@bywatersolutions.com