Refactors basket plugins and implements highlighting of items in basket and checkout summary in case of errors

- Implements highlighting of items in basket and checkout summary in case of errors
- Improves error handling of BasketLimits plugin and implements "max-value" and "max-products" (Incompatible: min-value must be an associative list with the currency IDs as keys)
- Replaces "Complete" plugin by "BasketLimits", adapts and migrates configuration
- Incompatible: Allows to distinguish errors in ProductGone plugin and streamlines error codes of ProductPrice and ProductStock plugin