ShoppingCart - add duplicate detection
ShoppingCart - add duplicate detection

this keeps each item's data in the cart too, and runs duplicate detection on every shopping cart change

https://bugzilla.redhat.com/show_bug.cgi?id=1377759

ManageIQ/manageiq-ui-service,ManageIQ/manageiq-ui-self_service,ManageIQ/manageiq-ui-self_service,AllenBW/manageiq-ui-service,dtaylor113/manageiq-ui-self_service,ManageIQ/manageiq-ui-self_service,AllenBW/manageiq-ui-service,dtaylor113/manageiq-ui-self_service,AllenBW/manageiq-ui-service,ManageIQ/manageiq-ui-service,ManageIQ/manageiq-ui-service,AllenBW/manageiq-ui-service,dtaylor113/manageiq-ui-self_service