Updated store checkout flow

We've been working on integrating Stripe as a payment provider into the store app. While we were working on that we realized that we needed to rethink how the checkout flow goes. The checkout flow used to follow these steps: - Cart - Shipping - Billing (and choose shipping method) - Review - Receipt In order to follow best practices with Stripe payments, the payment step needed to be last (right before the Receipt step). We are still working on the Stripe integration, but in preparation for it, we have gone ahead and revised the store checkout flow. This also involved updating all the websites that are currently using the Store app to support the new checkout flow. The new store checkout flow is: - Cart - Shipping Address - Shipping Method - Payment - Receipt We chose to put the process of choosing the shipping method for the order to its own step. This allows the payment step to focus only on payments. It also makes it a better flow if there are no shipping methods (i.e. free shipping), or there is a coupon for free shipping. The next store update will be in a few days when we complete the Stripe payment integration.