Remove public one-arg constructor magic

This pull request serves as a basis for discussion whether the feature introduced in xp-framework/rfc#243 that public one-arg constructors will be invoked for deserialization automagically should be kept or not. It covers the case for `lang.types.Number`, e.g., which could be handled separately, and removing it fails numerous tests, so **don't merge this!**.

@iigorr had a problem with this behaviour when he used more complex transfer objects.