Add Number of Open Requests to Item Table on Instance Record

Purpose: To make it easier to see at-a-glance how requested a title is (helpful in purchasing decisions). This feature was requested by Marie Widigson at Chalmers.

User story:
As an acquisitions librarian
I want to be able to look at an instance record and quickly see how requested its copies currently are
So I can assess its popularity and decide whether I should purchase more copies

Scenarios:

1. Scenario
   • Given the item table on the instance record
   • When displayed
   • Then a column should display for Requests
     • Count of open requests on item