* Improve RouteData and RouteDescription
* Remove asserts from code (at least where asserts can be provoked by user)
* Define a error code concept (possibly copy class Status form Illumination)
* Add text only interactive demo applications.
* Improve routing algorithm to check for routing to non-rechable targets
* Think about virtual vs. non-virtual methods.
* GenRelationDat:
  - It seems that the resolving step is the most time consuming.  Thus first
    detect type of Relation and decide if relation is relevant. Only if
    relation is relevant resolve the relation.
* GenWayDat:
  -  Improve performance of GenWayDat.
