Incorrect dependency from simulation and model debugging framework to trace

In the Architecture, simulation and model debugging framework is supposed to be independent of Trace
(as shown in the following figure)

However, the method [AbstractDSLDebuggerServices.currentInstructionChanged()](https://github.com/eclipse/gemoc-studio-modeldebugging/blob/master/simulationmodelanimation/plugins/org.eclipse.gemoc.dsl.debug.ide.sirius.ui/src/org/eclipse/gemoc/dsl/debug/ide/sirius/ui/services/AbstractDSLDebuggerServices.java) does add a dependency to trace.commons by using `Step`, `ParallelStep` and `MSEOccurrence`.

We should try to remove this dependency (by making sure to deal with these concepts in all subclasses of AbstractDSLDebuggerServices)