Bug 14057: Inventory is painfully slow

Bug 14057: Inventory is painfully slow

This patch is a rough start. I believe it runs exponentially
faster, but its equality to the previous version needs to be
tested before I clean it up to acceptable standards.

Nested hashes of hashes was being a debugging nightmare.

Moved the SQL select to C4::Koha.

Changed the GetItemsForInventory to have a hashref parameter.
Added interface, in case there is a need for 'opac' vs. 'staff'.

Added t/db_dependent/Items/GetItemsForInventory.t
Added t/db_dependent/Koha/GetKohaAuthorisedValuesMapping.t

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>