Bug 12975: Use the centralize VAT and prices calculation - basketgroup.pl

Bug 12975: Use the centralize VAT and prices calculation - basketgroup.pl

Bug 12969 introduces a subroutine to centralize VAT and prices
calculation.
It should be use in the acqui/basketgroup.pl script.

Test plan:
0/ Don't apply the patch
1/ Create 4 suppliers with the different configurations
2/ Create a basket and create several orders
3/ Close the basket and create the corresponding basket groups.
4/ Print the basket group
5/ Verify you don't see any difference before and after applying the
patch on the pdf file.

Signed-off-by: Paola Rossi <paola.rossi@cineca.it>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Works as described, passes tests and QA script.

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>