Select default frontend attribute behavior

Currently if an attribute used in an attribute-set is empty for a product it will display N/A or No on the frontend in the Attribute table. To allow more control over the shown data for the shop owner there is a new option empty_behavior (only visible when attribute is visible on frontend)

Options when attribute is empty:
Show N/A or No => Current behavior
Show default value (if available) => Shows the attribute default value or N/A / No
Hide if no default => Shows the attribute default or hide attribute if no default specified
Hide attribute => Hides the attribute on the frontend.