Ecore fixes for model checking #1288

The Ecore model is not populated with lower (and upper) bounds for attributes and references, e.g. IfcContext.RepresentationContexts or IfcCurveBoundedSurface.Boundaries. Cardinalities are only set for some defined types extending EXPRESS aggregates.

There are some other defincienciey and inconsistencies, which might be collected via this issue. Some issues are not fixable or require more intricate workarounds similar to the asymmetric inverses. One such example is IfcSiUnit.Dimensions overriding IfcNamedUnit.Dimensions.