Add internal name for stock locations.

Includes light refactoring of stock_locations/index.html.erb from Ryan Bigg.

Fixes #3532
Fetch deleted variant and product in line items

Fixes #3537
Add internal name for shipping_methods

Allows a place to store an internal name for a shipping method that helps associate the method to some backend context while still displaying a sensible name to shoppers.

Fixes #3533