Bug 12623: SQLHelper replacement - Borrower::Modifications

Bug 12623: SQLHelper replacement - Borrower::Modifications

With this patch, the subroutines AddModification and ApproveModifications uses DBIx::Class instead of C4::SQLHelper.
Moreover, the tests has been wrapped in a transaction.

Test plan:
1) Apply the patch

2) Execute the unit tests by launching :
prove t/db_dependent/Koha_borrower_modifications.t

3) The result has to be a success without error or warning :
t/db_dependent/Koha_borrower_modifications.t .. ok
All tests successful.
Files=1, Tests=14,  2 wallclock secs ( 0.03 usr  0.01 sys +  1.60 cusr  0.08 csys =  1.72 CPU)
Result: PASS

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>