made it a little bit easier for beginners by giving wesen a larger maximal age
Two internal changes of data structure:

* the big list of all objects is now stored in an id-indexed dict.
  in future, this should be kept internally as a map backed by a sorted list,
  to exploit the fact that we don't need to hash and can use the unique id for this.
* we don't use any object.copy() for our security model any longer,
  instead we use python's internal Proxy mechanism.
  This doesn't change any behaviour,
  but it will throw exceptions if someone tries to break the rules.
Adapting to the new dict-bases interface for the big list of all items;
This interface is not yet given to the wesen AIs.
Fixed several small errors and introducing nice __str__ representations.