Allow user to add multiple boxes/pallets at once

[jmiranda]

Reported by Martine:

Do we have an Openboxes feature that allows you to add multiple boxes at once to a pallet/shipment? Right now, I add each pallet, and boxes one by one. For big shipments, like one I have right now with 113 boxes in 2 pallets, it would save me a lot of time to add the boxes at once to the pallets.

[jmiranda]

We can do this in two ways:

• Add a dialog to the edit packing list to allow user to add multiple containers to a shipment or container
• Allow user to include pallet / box in the new import shipment items feature (Allow user to import items into shipment using XLS #37)

I'm going to try to implement both of these solutions

[jmiranda]

Duplicate of #48