Batch update items in inventory

[git-wil]

Goal

It can be useful to apply a batch update to many items in inventory, like modifying quantity, location, etc. for a large group of items. It would be convenient to have a method to batch-update items using a query and a mod to update all items that follow from that query.

Should be completed after #28.

Subtasks

• Define a discrete list of modifications that can be applied
• Define a query language/system for querying items (may be just by text, may be more complex)
• Create a popup/page/kiosk for inputting queries and batch updates
  • This should show a preview of the modifications before actually applying them
  • Would be nice to have an undo/backup feature, but may be difficult to implement