CSR UI: Manage shipping address (Beta)

Description

This story adds the following features to beta customers.

Display the cart's currently selected addresses
The shipment element of the cart view has a dropdown selector for the shipment's Shipping address.

Select an existing address
The dropdown lists existing addresses from the current customer's address book.

Create new addresses
At the top of the dropdowns, a button lets you add a new address. If an address is added, it is assigned as the current form's shipping address. The new address is also added and saved to the current user's Address Book.