Equivalent model for each core element

[franzlst]

Each core class should be represented 1-to-1 by a Model class. This is already the case for many, but not all elements. E.g. there is only a StateModel and ContainerStateModel, but not ExecutionStateModel or HierarchyStateModel.

Originally created by @franzlst ([email protected]) at 2017-12-05 12:04:28+00:00 (moved from RMC internal repository)