Easier inventory management

Today we've added some useful features to improve your inventory admin.

1. You can now quickly duplicate a stock item - fantastic for cloning common configurations to get new entries fast
2. You can split a stock item - great for situations when you need to split an initial entry into bundles, or when you want to track offcuts etc with new lengths
3. You can manage the location of stock - say where stock is to help people find it easier
4. Manage your stock locations - similar to the way you can manage materials and stock types, you can now manage locations
5. Roomier table view - the inventory now has expandable rows to help view everything more easily