[FIX] Set an empty array as default value for availableWebStoreIds parameter in WebStoreSelector block.
Update cart in the frontoffice order process
 - new action UpdateCart
 - new objects for coupons and shipping modes in cart (Rbs\Commerce\Process\BaseCoupon and Rbs\Commerce\Process\BaseShippingMode)
[FIX] Head menu dropdowns should be over the website navbar.
Merge pull request #787 from intportg/dev

Update cart during the frontoffice order process + fixes