Make static URLs absolute in handouts, updates, and about for mobile API

JIRA: MA-147
Revert "Make static URLs absolute in handouts, updates, and about for mobile API"

This reverts commit fb6579abfdb6fc9fb8bc9233554ff5c6e9215659.
Allowing email optin to work on register.
Improvements and bug fixes for shopping cart: WL-117, WL-114, WL-116, WL-115, WK-122
Code review comments
Merge pull request #5774 from edx/cdodge/shopping-cart-touchups

Cdodge/shopping cart touchups
Merge pull request #6138 from edx/sanchez/fix_register_email_opt_in

Allowing email optin to work on register.
Merge branch 'release'
add 'defunct' states for shoppingcart (ECOM-737)
add retire method to order class