Interim commit with a broken inventory counting. Will improve.
Laundry list of changes: Purchase Order Dialog no longer closes when you approve it; Inventory purchasing now picks the first available supplier, or Supplier A if none are available; Purchase Order View no longer crashes if a null supplier is passed; all status classes now have correlated constants; and above all, the new inventory system works as expected.
Added ReportView objects (tentative, will change).
Removed silly excess code in InventoryView.