Bug 18267: Refactored Edifact Price Calculations

Bug 18267: Refactored Edifact Price Calculations

Refactored the price calculations for Quotes and Invoices
This takes in to account various combinations used by different
vendors. Makes the extraction of basic price, quantity and tax
information more reliable. Tests are in Edifact.t and EdiInvoice.t

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit 36d46c6510ee93ffc52f6b914389c66351b16f33)

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>