Find a way to reduce the amount of shadow concepts in the language #10
Description
Currently, all relations are modeled explicitly using *Relation concepts. This could be reduced more, using nodesQuery or other smart mechanisms in order to render diagrams as much as possible based on the original information that already exists in jetbrains.mps.lang.structure.
This is useful, since it prevents having to keep the structure and the graphical structure information in sync (e.g. by using the sync intention).