Pull currency for Stripe from the settings file

With Stripe launching in different countries, the currency should be located in the configuration rather than hard coded in the processor
Adding Card Verification Field
Added Ryan Lander to AUTHORS.
Merge
Make STRIPE_CURRENCY setting backwards compatible.
Added www.zigzagbags.com.au to sites in README.
Add setting SHOP_ORDER_EMAIL_BCC

This should be set to an internal email address. All order receipt emails will be sent to this address via BCC, as well as being sent to the customer.
Ensure live stock lookup only uses unexpired carts.
Merge
New pt-BR translation
Cart should revert to old values if update not valid