Support for owner

[pauxus]

if A contains B and B holds an owner reference to A, the owner reference (B'.owner) should point to the containing instance of A' instead of creating a new one.

There are several options:

• Always use factories (A'.create) instead of constructor calls. This would allow some kind of caching of instances. Problem: this would be global, what about when you explicitly want different wrapper instances on the same delegate (for changeable wrappers)?
• Using some kind of ThreadLocal: When the first constructor of a Wrapper is called, a mapper is initialized. All Wrappers are registered there and the factory checks whether the delegate has already been wrapped, if yes, the wrapped instance is returned. Problem: what if the same instance is used in different contexts? (Corner case) - Also, this might mean that KlumWrap must be available at runtime (instead of compile time only), since we need a place to store this ThreadLocal)
• A Wrapper instance keeps references to all its direct wrapper children in a structure. When an inner wrapper ist instantiated, it is provided with its container as additional parameter. Whenever the child creates a wrapped instance, it is checked first against the container instance. This would mean rather complex logic
• KlumWrap could have a direct depedency to KlumAST and handle the owner annotation as a special case