SNode.getContainingModel() returns null when model is not attached
fix modelDescriptor ==/!= null in core code: java code
fix modelDescriptor ==/!= null in core code: MPS code
got rid of isinstanceof SModel
SModelInternal - required methods added
got rid of casts to SModel (except CopyUtil)
getSModel prepared for inlining
SNode.getModel prepared for inlining
FakeModelDescriptor.getModelDescriptor
SModel does not implement ISModel
SNode.getModel is ISModel
SNode.getModel is ISModel:generated code
SNode.getModel is a model descriptor
SModelDescriptor.getSModel returns ISModel
SModelDescriptor.getSModel returns model descriptor
more conservative SNode.getModel
fix compilation in MPS
fix refs in models
fix constraints tests
instanceof TransientSModel -> .getModule() instanceof TransientModelsModule