Increased flexibility in inventory integration

Overview:
In order to better accommodate the procedures of the various libraries, it's necessary for us to make the inventory integration a little more flexible. In order to accomplish this we're moving away from "create inventory/item" flags and will support two new enumeration fields. See MODORDERS-178 for details.

• Omit the new poLine.physical.createInventory and poLine.eresource.createInventory from the default mappings. Let mod-orders use the tenant (if set) or system defaults.
• Make necessary adjustments to allow for these fields to be mapped if desired.
• Update unit and API tests to exercise the mapping of these fields.

Acceptance Criteria:

• acq-models submodule updated
• buisness logic updated