2checkout fields fix

Rounds out a few missing mappings from #1012 
- Adds the `:shipping_address` `:name` field
- Maps `:address2` to `ship_street_address2` as mentioned the 2Checkout dev docs. 

From the original PR: 
> The `ship_name` field is currently missing so the buyer must enter it on 2Checkout's hosted page.

> If all billing information (and shipping information if applicable) is passed the `purchase_step` parameter can be passed with the name of the checkout step to display to the buyer when they arrive on 2Checkout's hosted page.
Possible values are ‘review-cart’, ‘shipping-information’, ‘shipping-method’, ‘billing-information’ and ‘payment-method’.
https://www.2checkout.com/documentation/checkout/parameter-sets/pass-through-products

> 2Checkout referral partners can optionally pass the `2co_cart_type` parameter to identify themselves or their cart software.

@odorcicd for review pls