Add Inventory dashboard

User will need to see:

• total items grouped by inventory_type in stock across all locations, with some kind of color indicator for when quantity is below 5
• inventory_type totals per location, with some kind of color indicator for when quantity is below 5
• include total Purchases (for purchases that have a box via shipping_payment)
• include total # of BoxRequests and Boxes shipped
• add start_date and end_date filters that filter the Purchases total, and Box and BoxRequest counts for easy reporting