Do not throw exception in methods not returning anything

Helps with TDD in other components. The handler is still obviously
incomplete.
Implemented: Recursive deep cloning in base value object

Not doing this, basically results in useless cloning behaviour, since
aggregated structs will still reference the same object. This results in
very subtle bugs, which happend in the SqlNG engine just now.
Configure SqlNG handler through service.ini
Removed usage of reflection to configure SqlNG repository
Added: Note about wrong author field type handling
Mark tests incomplete if gateway implementation is missing
Activate field external data handling